Method of manufacturing an optical member having stacked high and low refractive index layers

ABSTRACT

A method of making an optical member including high refractive index layers and low refractive index layers, which are each relatively thin as compared with an optical length, and disposed alternately in the lateral direction with respect to an optical axis. Each width of the high refractive index layers and the low refractive index layers is equal to or smaller than the wavelength order of incident light.

RELATED APPLICATION DATA

This application is a division of U.S. patent application Ser. No.12/132,042, filed Jun. 3, 2008, the entirety of which is incorporatedherein by reference to the extent permitted by law. The presentinvention claims priority to Japanese Patent Application No. JP2007-148165 filed in the Japanese Patent Office on Jun. 4, 2007, theentirety of which also is incorporated by reference herein to the extentpermitted by law.

BACKGROUND OF THE INVENTION

The present invention relates to an optical member, and a solid-stateimaging device employing this optical member, and a manufacturing methodthereof.

With solid-state imaging devices including CCD (Charge Coupled Device)and CMOS (Complementary Metal-oxide Semiconductor) sensors, it is commonto provide an optical member such as an on-chip lens (OCL: On Chip Lens,also referred to as a micro lens), inner lens, or the like, and tocondense incident light into a light reception portion. Here, as for theoptical member, a member having a refracted type lens configurationemploying Snell's law is employed.

Note however, with a refracted type lens configuration employing Snell'slaw, the lens itself is thick, such as around 1 μm or more, so whenapplying this configuration to the on-chip leans or inner condensinglens of a solid-state imaging device, the device upper layer becomesthick. Thus, undesirable light incidence (referred to as obliqueincident light) from adjacent pixels increases, color mixtures due tothis oblique incident light increases, and consequently, colorreproducibility deteriorates.

Also, existing fabricating processes of on-chip lenses and inner lensesinclude a great number of processes, such as reflowing resist, and soforth, and are complicated, and are high in costs. In addition, whenfabricating such a lens by reflow, only a spherical lens can befabricated, an asymmetrical lens shape, e.g., deformed in the lateraldirection cannot be fabricated.

Further, when reducing the F value of an external image formation systemlens, oblique incident light increases, the upper layer becomes thick,so deterioration from ideal sensitivity becomes pronounced, andaccordingly, the original sensitivity cannot be obtained (F value lightsensitivity deteriorates).

Also, with existing on-chip lenses, condensing efficiency deterioratesdepending on an incident angle. That is to say, light entered verticallyas to an on-chip lens can be condensed with high efficiency, butcondensing efficiency as to oblique incident light decreases. With asolid-state imaging device configured by multiple pixels being arrayedin a two-dimensional manner, in the case of incident light having aspread angle, incident angles differ between a pixel around the centerof solid-state imaging device and a pixel on the periphery thereof, andconsequently, a phenomenon wherein the condensing efficiency of thepixel on the periphery thereof deteriorates as compared with the pixelaround the center thereof, i.e., a phenomenon wherein sensitivitydecreases at an end of the device as compared with the center of thedevice (shading) becomes pronounced.

With regard to deterioration in color reproducibility due to obliqueincident light, performing calculation processing for restoring thecolor reproducibility can be conceived, but may result in a negativeeffect wherein extra noise is caused, and image quality deteriorates.

Further, when reducing the F value of an external image formation systemlens, an F value light sensitivity deterioration phenomenon is causedwherein oblique incident light increases, so the upper layer becomesthick, and deterioration from ideal sensitivity becomes pronounced, andconsequently, the original sensitivity cannot be obtained.

On the other hand, as one technique for solving a problem wherein theupper layer becomes thick, and deterioration in sensitivity, anarrangement employing a Fresnel lens has been proposed (e.g., seeJapanese Unexamined Patent Application Publication No. 2005-011969 andJapanese Unexamined Patent Application Publication No. 2006-351972).

For example, with the arrangement described in Japanese UnexaminedPatent Application Publication No. 2005-011969, an inner condensing lensfor further converging light converged on an upper portion lens such asan on-chip lens, and entering this into a photoelectric conversion unit,is configured based on a Fresnel lens. This lens has a feature in thatthis lens is a refracted type lens, but can be reduced in thickness bybeing formed as a wave type.

Also, with the arrangement described in Japanese Unexamined PatentApplication Publication No. 2006-351972, a condensing element isconfigured of a combination of multiple zone regions having a concentricconfiguration which is divided with a line width equal to or smallerthan the wavelength of incident light. This has a feature in that thecondensing element is configured with a distribution refractive indexlens (i.e., Fresnel lens) having a two-step concentric circleconfiguration as the basis.

Note however, the arrangement described in Japanese Unexamined PatentApplication Publication No. 2005-011969 is based on the Fresnel lensconcept, and accordingly, this Fresnel lens is a refracted type, sothere is limitation in reduction of the thickness thereof as comparedwith the wavelength order.

Also, in order to fabricate such a wave type requires a process evenmore complicated than the normal refracted type lens process, furtherraising costs. Also, only spherical-face lenses can be fabricated, soasymmetry cannot be introduced in designing.

In addition, each arrangement of Japanese Unexamined Patent ApplicationPublication No. 2005-011969 and Japanese Unexamined Patent ApplicationPublication No. 2006-351972 as well, is based on a Fresnel lens, solight obliquely entered in a certain region is not condensed into apoint to be condensed originally in some cases (details will bedescribed later). This decreases condensing efficiency, and also causesa color mixture in a case wherein diffused light enters in an adjacentpixel.

SUMMARY OF THE INVENTION

There has been recognized a need to provide a new optical memberarrangement. In a case wherein high refractive index layers and lowrefractive index layers which are relatively thin as compared with anoptical length (lens length) are arrayed alternately in the lateraldirection of an optical member (an arbitrary direction on a planeperpendicular to the optical axis), when each width of the highrefractive index layers and low refractive index layers is sufficientlygreater than the wavelength order of incident light, the equiphase wavesurfaces of the light passing through the optical member are formed inthe same way as the equiphase wave surface of the medium at the incidentside, and are not curved.

Note however, when each width of the high refractive index layers andlow refractive index layers is equal to or smaller than the wavelengthorder of incident light, according to continuity of a wave function, awave surface within a low refractive index layer and a wave surfacewithin a high refractive index layer are linked, and consequently, aphenomenon is caused wherein the overall equiphase wave surfaces arecurved.

An optical member according to an embodiment of the present invention isconfigured based on the above-mentioned observation. That is to say,with an embodiment of an optical member according to the presentinvention, high refractive index layers having a great refractive indexand low refractive index layers having a small refractive index, whichare each relatively thin as compared with an optical length, aredisposed alternately in the lateral direction as to an optical axis.Here, each width of the high refractive index layers and the lowrefractive index layers is equal to or smaller than the wavelength orderof incident light.

In the event of providing a function as an optical member by arrayingthe low refractive index layers and high refractive index layers eachhaving a width equal to or smaller than the wavelength order, the curvecondition of a equiphase wave surface can be adjusted by adjusting thelocation relation of each density of the high refractive index layers atthe center and end portion of the member.

Thus, if a convex lens function (condensing property) can be provided, aconcave lens function (diffusion property) can also be provided. Also, afunction for converting oblique incident light into vertical incidentlight (oblique light correction function) can be provided as well.Consequently, an optical member (optical lens) having a new arrangementcan be realized whereby the curve state of an equiphase wave surface(wave surface) can be controlled by adjusting each array width of thelow refractive index layers and high refractive index layers.

For example, the high refractive index layers may be each disposedsymmetrically so as to be disposed densely at the mechanical center ofthe member, and disposed non-densely farther away from the center,thereby serving as a convex lens function (condensing property). Asviewed from the low refractive index layers, the low refractive indexlayers are each disposed symmetrically so as to be disposed non-denselyat the mechanical center of the member, and disposed densely fartheraway from the center, thereby serving as a convex lens function(condensing property).

The high refractive index layers are each disposed symmetrically so asto be disposed non-densely at the mechanical center of the member, anddisposed densely farther away from the center, thereby serving as aconcave lens function (diffusion property). As viewed from the lowrefractive index layers, the low refractive index layers are eachdisposed symmetrically so as to be disposed densely at the mechanicalcenter of the member, and disposed non-densely farther away from thecenter, thereby serving as a concave lens function (diffusion property).

Each width of at least one kind of layer of the high refractive indexlayers and the low refractive index layers may be disposedasymmetrically in the lateral direction, thereby serving as an obliquelight correction function.

Such an optical member can be used as an independent member instead ofan existing common optical lens employed for a laser scanning opticalsystem or the like.

Note however, as for a combination with a solid-state imaging device, itis desirable to form the optical member integral with on a semiconductorsubstrate where a pixel array unit and so forth are formed.

The solid-state imaging device may be configured as a one-chip device,or may be configured as a module having an imaging function wherein animaging unit and a signal processing unit or optical system are packagedtogether.

Also, the present invention can be applied to not only a solid-stateimaging device but also an imaging device. In this case, as the imagingdevice, the same advantage as that in the solid-state imaging device canbe obtained. Here, the imaging device means, for example, a camera (orcamera system) or portable device having an imaging function. Also, theterm “imaging” is not restricted to capturing of an image at the time ofcommon camera shooting, but also includes fingerprint detection as ameaning in a broad sense.

According to an embodiment of the present invention, an optical memberis configured by arraying high refractive index layers and lowrefractive index layers, which are equal to or smaller than thewavelength order of incident light, thinner than the lens length,alternately in the lateral direction as to the optical axis, whereby theequiphase wave surfaces can be curved according to the array state ofeach width of the high refractive index layers and low refractive indexlayers when the incident light passes through the optical member.Consequently, the optical member exhibits the optical propertycorresponding to the array state of each width of the high refractiveindex layers and low refractive index layers (e.g., condensing function,diffusion function, or incident angle conversion function).

Thus, as for the optical member where the high refractive index layersand low refractive index layers are arrayed alternately in the lateraldirection, a member shorter and thinner than the optical length can beemployed, and a thin member can be employed as compared with a memberhaving a refracted type lens configuration employing the existingSnell's law. Consequently, problems caused in a lens having a relativelythick configuration, such as an existing lens, can be alleviated oreliminated.

For example, the upper layer of an imaging device is thinned, and colormixtures decrease, thereby improving color reproducibility. There is noneed to provide measures for color mixtures due to calculationprocessing, thereby reducing extra noise occurrence. Also, deteriorationin F value light sensitivity can be prevented, and oblique incidentlight can be corrected to vertical incident light, thereby providingmeasures for shading.

Also, the member is configured by the thin low refractive index layersand thin high refractive index layers being arrayed alternately, therebyproviding no step having a great refractive index such as a Fresnellens, and reducing diffusing light due to refraction or reflection as tooblique incident light. Consequently, condensing efficiency can beimproved, and a problem of color mixtures due to oblique incident lightcan also be solved.

Simply arraying the thin low refractive index layers and thin highrefractive index layers alternately in the lateral direction enablesmanufacturing in accordance with semiconductor processes, and cost canbe suppressed low with a simple fabrication process.

The optical property can be controlled by adjusting each array width ofthe low refractive index layers and high refractive index layers, andaccordingly, there is provided an advantage wherein the width ofdesigning can optically spread as compared with a spherical lens.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a diagram (Part 1) illustrating equiphase wave surfaces fordescribing the basic principle of an optical lens according to a firstembodiment;

FIG. 1B is a diagram (Part 2) illustrating equiphase wave surfaces fordescribing the basic principle of the optical lens according to thefirst embodiment;

FIGS. 1C through 1F are plan schematic views of the optical lensaccording to the first embodiment;

FIG. 2A is a cross-sectional schematic view for describing a firstexample (application example 1) of a solid-state imaging device to whichthe optical lens according to the first embodiment is applied;

FIG. 2B is a more specific cross-sectional view of the solid-stateimaging device according to the first embodiment (application example1);

FIG. 2C is a diagram (in the middle of the process) illustrating thesimulation result of the first embodiment (application example 1);

FIG. 2D is a diagram illustrating the simulation result of the firstembodiment (application example 1) (λ=780, 640 nm);

FIG. 2E is a diagram illustrating the simulation result of the firstembodiment (application example 1) (λ=540, 480 nm);

FIG. 3A is a cross-sectional schematic view for describing a secondexample (application example 2) of the solid-state imaging device towhich the optical lens according to the first embodiment is applied;

FIG. 3B is a diagram illustrating the simulation result of the firstembodiment (application example 2) (λ=780, 640 nm);

FIG. 3C is a diagram illustrating the simulation result of the firstembodiment (application example 2) (λ=540, 480 nm);

FIG. 4A is a cross-sectional schematic view for describing a thirdexample (application example 3) of the solid-state imaging device towhich the optical lens according to the first embodiment is applied;

FIG. 4B is a diagram illustrating the simulation result of the firstembodiment (application example 3) (λ=780, 640 nm);

FIG. 4C is a diagram illustrating the simulation result of the firstembodiment (application example 3) (λ=540, 480 nm);

FIG. 5A is a cross-sectional schematic view for describing a fourthexample (application example 4) of the solid-state imaging device towhich the optical lens according to the first embodiment is applied;

FIG. 5B is a more specific cross-sectional view of the solid-stateimaging device according to the first embodiment (application example4);

FIG. 5C is a diagram illustrating the simulation result of the firstembodiment (application example 4) (λ=780, 640 nm);

FIG. 5D is a diagram illustrating the simulation result of the firstembodiment (application example 4) (λ=540, 480 nm);

FIG. 6A is a diagram for describing a first comparative example as to aconvex lens according to an alternate placement layer of the firstembodiment;

FIG. 6B is a diagram for describing a second comparative example as tothe convex lens according to the alternate placement layer of the firstembodiment;

FIG. 6C is a diagram for describing a third comparative example as tothe convex lens according to the alternate placement layer of the firstembodiment;

FIG. 7A is a cross-sectional schematic view for describing a solid-stateimaging device according to modification 1 to which modification 1 ofthe optical lens according to the first embodiment is applied;

FIG. 7B is a diagram illustrating the simulation result of modification1 (λ=540 nm);

FIG. 8A is a cross-sectional schematic view for describing a solid-stateimaging device according to modification 2 to which modification 2 ofthe optical lens according to the first embodiment is applied;

FIG. 8B is a diagram illustrating the simulation result of modification2 (λ=540 nm);

FIG. 9 is a diagram illustrating the simulation result when obliqueincident light is entered with the configuration of the first embodiment(e.g., application example 1 in FIG. 2A);

FIG. 10A is a diagram illustrating equiphase wave surfaces fordescribing the basic principle of an optical lens according to a secondembodiment;

FIG. 10B is a diagram for describing a light reception optical system ofa solid-state imaging device;

FIG. 10C is a plan schematic view equivalent to a single optical lensaccording to the second embodiment;

FIG. 10D is a plan schematic view in a case wherein the optical lensaccording to the second embodiment is applied onto the pixel array unitof the solid-state imaging device;

FIG. 11A is a cross-sectional schematic view for describing thesolid-state imaging device to which the optical lens according to thesecond embodiment is applied;

FIG. 11B is a diagram illustrating the simulation result of thesolid-state imaging device according to the second embodiment (λ=540);

FIG. 12A is a diagram illustrating equiphase wave surfaces fordescribing the basic principle of an optical lens according to a thirdembodiment;

FIG. 12B is a diagram for describing the center of gravity of a lens;

FIGS. 12C through 12F are plan schematic views (Part 1) of a solid-stateimaging device to which the optical lens according to the thirdembodiment is applied;

FIGS. 12G through 12H are plan schematic views (Part 2) of thesolid-state imaging device to which the optical lens according to thethird embodiment is applied;

FIG. 13A is a cross-sectional schematic view for describing a firstexample (application example 1) of the solid-state imaging device towhich the optical lens according to the third embodiment is applied;

FIG. 13B is a diagram illustrating the simulation result of the thirdembodiment (application example 1) (λ=540 nm);

FIGS. 14A and 14B are circuit diagrams for describing a second example(application example 2: CMOS response) of the solid-state imaging deviceto which the optical lens according to the third embodiment is applied;

FIG. 14C is a plan schematic view of an alternate placement layerapplied onto the pixel array unit of the solid-state imaging deviceaccording to the third embodiment (application example 2);

FIGS. 15A and 15B are circuit diagrams for describing a third example(application example 3: CCD response) of the solid-state imaging deviceto which the optical lens according to the third embodiment is applied;

FIG. 15C is a cross-sectional configuration view in the vicinity of thesubstrate surface of the solid-state imaging device according to thethird embodiment (application example 3);

FIG. 15D is a plan schematic view of an alternate placement layerapplied onto the pixel array unit of the solid-state imaging deviceaccording to the third embodiment (application example 3);

FIG. 16 is a diagram illustrating equiphase wave surfaces for describingthe basic principle of an optical lens according to a fourth embodiment;

FIG. 17A is a conceptual diagram for describing a manufacturing processaccording to the present embodiment in a case wherein alternateplacement layers according to the first through fourth embodiments areformed integral with the solid-state imaging device;

FIG. 17B is a conceptual diagram for describing a comparative example asto the manufacturing process according to the present embodiment (in thecase of inner lens formation); and

FIG. 17C is a conceptual diagram for describing a comparative example asto the manufacturing process according to the present embodiment (in thecase of on-chip lens formation).

DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

Description will be made below regarding embodiments of the presentinvention with reference to the drawings.

First Embodiment Fundamentals of Convex Lens

FIGS. 1A through 1F are diagrams for describing the basic principle of afirst embodiment of an optical lens. Here, FIGS. 1A and 1B are diagramsillustrating equiphase wave surfaces, and FIGS. 1C through 1F are planschematic views of the optical lens according to the first embodiment.

Each optical lens of the present embodiment including later-describedother embodiments includes a lens function basically by arrayingrectangular layers having a great refractive index and rectangularlayers having a small refractive index alternately in the lateraldirection as to the optical axis, and each width thereof beingconfigured so as to be equal to or smaller than the wavelength order.

For example, “the configuration of width equal to or smaller than thewavelength order” can be formed by employing the arrangement of acondensing element having a subwave length periodical structure (SWLL:Subwave Length Lens) formed by using planar process technologyrepresented by optical lithography and electron lithography.

An SWLL is employed as a condensing element for a solid-state imagingdevice, whereby an on-chip lens can be formed with a commonsemiconductor process, and the shape of the lens can be control withoutlimitation.

Here, the first embodiment relates to a convex lens having a condensingeffect. Accordingly, high refractive index layers are configuredsymmetrically in a plate shape so as to be disposed densely at thecenter (mechanical center of the lens: identical to the optical axis inthe present example), and disposed non-densely farther away from thecenter. From the aspect of layers having a small refractive index, lowrefractive index layers are configured symmetrically so as to bedisposed non-densely at the mechanical center of the member, anddisposed more densely away from the center. The first embodiment differsfrom later-described second and third embodiments in that the lens issymmetrical (has a symmetrical configuration).

In order to provide a convex lens function by employing a configurationwherein density increases toward the center and decreases farther awayfrom the center, for example, it is desirable to employ one of a firstconvex lens proving method wherein the widths of high refractive indexlayers increase gradually toward the center of a lens, a second convexlens providing method wherein widths of low refractive index layersdecrease gradually toward the center of a lens, and a third convex lensproviding method wherein the first convex lens providing method andsecond convex lens providing method are employed together. From theperspective of condensing efficiency, it is most effective to employ thethird convex lens providing method.

First, as shown in FIG. 1A, let us say that a plate-shaped singlematerial layer 1 having a refractive index n0 alone exists, and adjacentthereto (specifically, equiphase wave surface 1_4 side) a plate-shapedlayer (referred to as an alternate placement layer) 2A is providedwherein rectangular layers (referred to as low refractive index layers)20 having the refractive index n0, and rectangular layers (referred toas high refractive index layers) 21 having a refractive index n1(wherein n1>n0), which is higher (greater) than the refractive index n0,are arrayed alternately in the lateral direction. Let us say that aplate-shaped single material layer 3 having the refractive index n0alone is provided further backward the alternate placement layer 2A.Though details will be described later, the alternate placement layer 2Aserves as an optical lens (convex lens) having condensing efficiency.

With the alternate placement layer 2A, the components on the right sideof the optical center CL are denoted with “R”, and the components on theleft side thereof are denoted with “L”. When there is no need todistinguish the right side and left side, description will be made byomitting “R” and “L”. These are the same as those in later-describedother examples.

With the configuration of the basic example of the first embodimentshown in the drawing, five rectangular high refractive index layers 21having a great refractive index are provided symmetrically as to thecenter CL, and four low refractive index layers 20 having a smallrefractive index are provided therebetween. The widths of the highrefractive index layers 21R_1 through 21R_5, and 21L_1 through 21L_5 areconfigured so as to increase gradually toward the center CL, and thewidths of the low refractive index layers 20R_1 through 20R_4, and 20L_1through 20L_4 are configured so as to decrease gradually toward thecenter CL. That is to say, with the basic example of the firstembodiment, the third convex lens providing method wherein the first andsecond convex lens providing methods are employed together is employed.

As a whole, the alternate placement layer 2A has a configuration whereinthe high refractive index layers 21R_k and 21L_k (k=1 through 5 in thepresent example) having a great refractive index are disposed in a plateshape, disposed densely at the center, and disposed non-densely fartheraway from the center. When focusing on the high refractive index layers21, the widths thereof are wide at the center of the lens, and arenarrow in the vicinity.

Now, as shown in FIG. 1A, let us say that light enters from the singlematerial layer 1 side having the refractive index n0. At this time,velocity of light c is obtained by c=c0/n1. Here, c0 is velocity oflight in vacuo. Accordingly, with each of the high refractive indexlayers 21 of the plate-shaped alternate placement layer 2A, it can beconceived that velocity of light decreases therein, and consequently, asshown in FIG. 1A, the same equiphase wave surface (wave surface) as thesingle material layer 1 is formed. Note however, when the lengths (i.e.,widths) in the lateral direction of the high refractive index layers 21having the high refractive index n1 and the low refractive index layers20 having a small refractive index adjacent thereto are greater than thewave length order.

On the other hand, in a case wherein the lengths (widths) in the lateraldirection of the high refractive index layers 21 having the highrefractive index n1 and the low refractive index layers 20 having asmall refractive index adjacent thereto are equal to or smaller than thewave length order, the same equiphase wave surface (wave surface) as thesingle material layer 1 is not formed, and the wave surface are curveddepending on how the widths of the high refractive index layers 21 andthe low refractive index layers 20 adjacent thereto are arrayed.

Specifically, according to the continuity of a wave function, a wavesurface within the low refractive index layer 20 _(—) j and a wavesurface within the high refractive index layer 21 _(—) k are linkedconsecutively, and consequently, all of the equiphase wave surfaces arecurved. As shown in FIG. 1A, in a case wherein the high refractive indexlayer 21 _(—) k having a great refractive index is configured in a plateshape so as to be disposed densely at the center, and disposednon-densely farther away from the center, the equiphase wave surfacesbecome those shown in FIGS. 1C through 1F. The cause of this is that thevelocity of light at the places having a great refractive index (highrefractive index layers 21) differs from that at the places having asmall refractive index (low refractive index layers 20).

As can be understood from the drawing, the wave surface of the lightbecome a recessed surface according to the alternate placement layer 2A,and this passes through the single material layer 3 having therefractive index n0 alone disposed in the backward thereof.Consequently, as shown in the drawing, a function is activated whereinthe route of the incident light is converted into the center side at theleft and right sides with the lens center as the boundary thereof,whereby condensing property can be provided. A convex lens effect can bereceived by combining the difference between the velocity of light ofthe high refractive index layers 21 having a great refractive index andthe velocity of light of the low refractive index layers 20 having asmall refractive index, and continuity of the wave function.

As can be understood from the above description, the optical lensaccording to the first embodiment can serve as a convex lens havingcondensing property by arraying the high refractive index layer 21 _(—)k having a great refractive index and the high refractive index layer 20_(—) j having a small refractive index alternately in the lateraldirection in a rectangular shape with the widths thereof beingconfigured so as to be equal or smaller than the wavelength order, andat this time, providing a configuration wherein the high refractiveindex layer 21 _(—) k having a great refractive index is disposeddensely at the center, and disposed non-densely farther away from thecenter.

The wave surface is curved depending on how the widths of the highrefractive index layers 21 having the high refractive index n1, and thelow refractive index layers 20 having a low refractive index arearrayed, so the curve level of the wave surface of light can becontrolled by adjusting how to array each of the widths, andconsequently, the condensing property of the convex lens can becontrolled. That is to say, it can be conceived that the alternateplacement layer 2A according to the first embodiment is a condensinglens (i.e., convex lens) employing the wave surface control arrangement.

As can be understood from the configurations shown in FIG. 1B, the lensthickness thereof is the thickness of the alternate placement layer 2Awherein the high refractive index layer 21 _(—) k having a greatrefractive index and the rectangular low refractive index layer 20 _(—)j having a small refractive index are arrayed alternately in the lateraldirection, whereby an extremely thin convex lens can be obtained. Forexample, with the refractive type lens configuration employing theexisting Snell's law, the lens thickness is equal to or greater than 1μm, but the thickness of the lens can be reduced to be equal to orsmaller than 0.5 μm by employing the optical lens according to thearrangement of the present embodiment.

If the lens thickness can be thinned, in the case of applying this lensto a solid-state imaging device, the upper layer becomes thin, wherebycolor mixtures decreases, and accordingly, color reproducibilityimproves. Also, color mixtures decreases, so there is no need to providecalculation processing for restoring color reproducibility, and extranoise occurrence due to the calculation processing also decreases. Alsothe lens thickness is thin, so even in a case wherein the F value of anexternal image formation system lens is reduced, oblique incident lightdoes not increase, a problem of deterioration in F value lightsensitivity is not caused.

It goes without saying that with a plan configuration as well, thealternate placement layer 2A needs to have a configuration wherein thedensity is high at the center and becomes low farther away from thecenter, and only in this case, various plan configurations can beemployed. As for each shape of the high refractive index layer 21 _(—) khaving a great refractive index and the low refractive index layer 20_(—) j having a small refractive index, any arbitrary shape can beemployed, such as a circle, ellipse, regular square, rectangle,triangle, or the like. Subsequently, of these, a shape can be regardedas the same is converted into a circular shape, or different shapes arecombined and converted into a circular shape such that the widths ofeach ring are the same vertically and horizontally.

For example, as shown in FIG. 1C, the high refractive index layer 21_(—) k and low refractive index layer 20 _(—) j may be each circles orcircular ring shapes, each closing on itself. As shown in FIG. 1D, thehigh refractive index layer 21 _(—) k and low refractive index layer 20_(—) j may be each ellipses or elliptic ring shapes, each closing onitself. As shown in FIG. 1E, the high refractive index layer 21 _(—) kand low refractive index layer 20 _(—) j may be each regular squares orsquare ring shapes, each closing on itself. As shown in FIG. 1F, thehigh refractive index layer 21 _(—) k and low refractive index layer 20_(—) j may be each rectangles or rectangular ring shapes, each closingon itself.

Though not shown in the drawing, the high refractive index layer 21 _(—)k and low refractive index layer 20 _(—) j may be each triangles ortriangular ring shapes, each closing on itself. Also, though not shownin the drawing, for example, an arrangement may be made whereindifferent shapes are employed at the center and at the outercircumference, such that circles or circular ring shapes are employed atthe center, and rectangular ring shapes are employed at the outercircumference, and these are combined, thereby each closing on itself.

Note however, the condensing effect as a convex lens is influenced bythe plan configuration of the alternate placement layer 2A, i.e., theplan configuration of how the high refractive index layers 21 and lowrefractive index layers 20 are arrayed, so in the case of applying theabove-mentioned shapes to a solid-state imaging device, it is desirablethat the plan configuration exemplified in FIGS. 1C through 1F,particularly the shape of the high refractive index layer 21_1 at thecenter portion is matched to the plan shape of the light receptionportion.

First Embodiment Application Example 1 of Convex Lens

FIGS. 2A through 2E are diagrams for describing a first example(application example 1) of the solid-state imagining device to which theoptical lens according to the first embodiment is applied. Here, FIG. 2Ais the cross-sectional schematic view of the solid-state imaging deviceaccording to application example 1, FIG. 2B is a more specificcross-sectional view of the solid-state imaging device according to thefirst embodiment (application example 1), and FIGS. 2C through 2E arediagrams illustrating the simulation results of the optical propertythereof.

A solid-state imaging device 100A according to the first embodiment(application example 1) includes a thin-film layer 130 (thickness=0.1μm) made up of silicon nitride Si3N4 (hereafter, referred to as SiN)with a refractive index n1 of 2.0 on a semiconductor substrate(hereafter, also referred to as a silicon substrate) 102 made up ofsilicon Si with a refractive index n3 of 4.1 and an extinctioncoefficient (coefficient related to absorption of light) k of 0.04, andon the upper layer thereof includes an optical lens 110A having theconfiguration (alternate placement layer 112A) described with referenceto FIGS. 1A through 1F as the principal portion.

The thin-film layer 130 is provided as an antireflection film as to thesilicon substrate 102. Thus, light can be entered in the light receptionportion, such as a photodiode, effectively. For example, if we say thatthe refractive indexes of the silicon Si, silicon nitride SiN, andsilicon oxide SiO2 are n_Si, n_SiN, and n_SiO2, respectively, a relationn_Si>n_SiN>n_SiO2 holds. In this case, the thickness d of the thin-filmlayer 130 has a relation of d≠λ×(m/2+1/4)/n_SiN, so an antireflectionfilm function can be performed effectively. Here, λ is the wavelength oflight, and m is an integer equal to or greater than 0.

As shown in FIG. 2B, photoelectric conversion units (light receptionportions) 104 made up of PN junction are disposed with a predeterminedpixel pitch on the boundary neighborhood (substrate surface) at theoptical lens 110A side of the silicon substrate 102. The solid-stateimaging device 100A includes a pixel array unit formed by regularlyarraying the multiple (e.g., several millions) photoelectric conversionunits 104 vertically and horizontally or in an oblique direction.

A color filter 106 and on-chip lens 108 are provided on the upper layerat the light incident face of the optical lens 110A as necessary. Theon-chip lens 108 is a lens having a refracted type lens configurationemploying Snell's law.

With the example shown in FIG. 2B, an example is illustrated wherein theon-chip lens 108 is employed as an upper layer lens (surface lens), andthe alternate placement layer 112A of the optical lens 110A is employedas an inner condensing lens, but the on-chip lens 108 can also bereplaced with the alternate placement layer 112A. In this case, thealternate placement layer 112A is not embedded within the device upperlayer, but is disposed on the uppermost layer of the device as a lensconfiguration, and the surface thereof is in contact with the air.

The on-chip lens 108 is a lens having a refracted type lensconfiguration employing Snell's law, the lens itself is around 1 μm,thick, so the device upper layer becomes thick, and a problem of colormixtures due to oblique incident light can be caused, but this problemcan be decreased by replacing the on-chip lens 108 with the alternateplacement layer 112A.

The example shown in FIG. 2B illustrates a state of the peripheralportion of the pixel array unit, wherein the center of the on-chip lens108 and the center of the alternate placement layer 112A equivalent toone cycle worth of the optical lens 110A are shifted and disposed suchthat the oblique incident light passed through the on-chip lens 108passes through the center of the alternate placement layer 112A.However, such an arrangement is not necessary at the center portion ofthe pixel array unit, so the center of the on-chip lens 108 and thecenter of the alternate placement layer 112A equivalent to one cycleworth of the optical lens 110A are disposed so as to be identical.

Though detailed description will be omitted here, a wiring layer 109 isprovided between the alternate placement layer 112A and the surface(thin-film layer 130 side) of the silicon substrate 102. With the wiringlayer 109, aluminum wiring for controlling the charge storage operationand signal readout operation of each photoelectric conversion unit 104is provided so as not to prevent the optical path to the photoelectricconversion units 104.

The optical lens 110A includes a thick layer of silicon oxide SiO2(referred to as a silicon oxide layer) with the refractive index n1 of1.46 as a medium, and includes the alternate placement layer 112A havingthe same configuration as the alternate placement layer 2A describedwith reference to FIGS. 1A through 1F on the surface neighborhood at thelight incident side thereof. The light incident side from the alternateplacement layer 112A serves as a single material layer 111 similar tothe single material layer 1 described with reference to FIGS. 1A through1F, and the silicon substrate 102 side from the alternate placementlayer 112A serves as a single material layer 113 similar to the singlematerial layer 3 described with reference to FIGS. 1A through 1F.

One cycle (i.e., lens size) of the optical lens 110A is adjusted to apixel size (=pixel pitch) of 3.6 μm. The distance (thickness:substantial lens length) from the boundary surface between the siliconsubstrate 102 and thin-film layer 130 to the alternate placement layer112A is set to 3.6 μm, and the thickness (substantial lens thickness) ofthe alternate placement layer 112A is set to 0.5 μm. As can beunderstood from this as well, the alternate placement layer 2Aconfigured by the high refractive index layer 21 _(—) k and lowrefractive index layer 20 _(—) j being arrayed alternately is setsufficiently thinner than the optical length (lens length).

With the alternate placement layer 112A, rectangular low refractiveindex layers 120 of silicon oxide SiO2 with the refractive index n0 of1.46, and rectangular high refractive index layers 121 of siliconnitride SiN with the refractive index n1 of 2.0 are disposed such thatthe widths of the high refractive index layers 121 increase graduallytoward the center of the lens, and the low refractive index layers 120decrease gradually toward the center of the lens, thereby configuringthe high refractive index layers 121 in a plate shape so as to bedisposed densely at the center and disposed non-densely farther awayfrom the center.

With the first embodiment (application example 1), the widths of the lowrefractive index layer 120 _(—) j and high refractive index layer 121_(—) k (both are not shown in the drawing) within the alternateplacement layer 112A during one cycle, and the boundary distance (thesynthetic width of the adjacent low refractive index layers 120R_5 and120L_5 in the present example) are set as follows.

high refractive index layer 121R_1+high refractive index layer 121L_1:0.45 μm

high refractive index layer 121R_2, high refractive index layer 121L_2:0.25 μm

high refractive index layer 121R_3, high refractive index layer 121L_3:0.20 μm

high refractive index layer 121R_4, high refractive index layer 121L_4:0.15 μm

high refractive index layer 121R_5, high refractive index layer 121L_5:0.10 μm

low refractive index layer 120R_1, low refractive index layer 120L_1:0.10 μm

low refractive index layer 120R_2, low refractive index layer 120L_2:0.15 μm

low refractive index layer 120R_3, low refractive index layer 120L_3:0.20 μm

low refractive index layer 120R_4, low refractive index layer 120L_4:0.225 μm

low refractive index layer 120R_5+low refractive index layer 120L_5:0.40 μm

As can be understood from the drawing, the alternate placement layer112A of the optical lens 110A is a condensing element having a SWLLconfiguration wherein incident light is curved with the periodicstructure of the low refractive layers 120 made up of silicon oxide SiO2having a refractive index of 1.46, and the high refractive layers 121made up of silicon nitride SiN having a refractive index of 2.0. In thepresent example, with the alternate placement layer 112A having theperiodic structure of silicon nitride SiN and silicon oxide SiO2, bothof the low refractive index layers 120 and high refractive index layers121 are configured such that the minimum line width in the lateraldirection is 0.1 μm, and the lens thickness is 0.5 μm.

FIG. 2C illustrates the simulation result regarding green light having awavelength λ of 540 nm passing through the optical lens 110A shown inFIG. 2A. In the drawing, cT is obtained by multiplying velocity of lightc by time T, and represents distance where the light advances in vacuo(increments: μm). Here, this may be regarded as the time which thesimulation took.

First, (1) in FIG. 2C shows the simulation result immediately after thelight passes through the alternate placement layer 112A of the opticallens 110A shown in FIG. 2A. It can be understood from this result thatthe wave surfaces of front (silicon substrate 102 side) of the greenlight passed through the alternate placement layer 112A are recessedsurfaces.

In FIG. 2C, (2) shows the simulation result when the light passesthrough the alternate placement layer 112A, and further generallyreaches the surface of the silicon substrate 102 (i.e., photoelectricconversion element). It can be understood from this result that thegreen light condenses to the center of each optical lens 110A, and thereis a convex lens effect regarding the green light (λ=540 nm). Thoughomitted in the drawing, there is similarly a lens effect regardingnear-infrared light (λ=780 nm), red light (λ=640 nm), and blue light(λ=460 nm).

FIGS. 2D and 2E are diagrams illustrating the simulation resultsregarding the solid-state imaging device 100A according to the firstembodiment (application example 1) to which an optical lens having thesame configuration as the optical lens 110A according to the firstembodiment (application example 1) shown in FIG. 2A, and represent theresults of near-infrared light (λ=780 nm), red light (λ=640 nm), greenlight (λ=540 nm), and blue light (λ=460 nm), respectively. As can beunderstood from these, light having any wavelength is condensed with theoptical lens 110A, thereby providing a convex lens effect.

First Embodiment Application Example 2 of Convex Lens

FIGS. 3A through 3C are diagrams for describing a second example(application example 2) of the solid-state imagining device to which theoptical lens according to the first embodiment is applied. Here, FIG. 3Ais the cross-sectional schematic view of the solid-state imaging deviceaccording to the first embodiment (application example 2), and FIGS. 3Band 3C are diagrams illustrating the simulation results of the opticalproperty thereof.

The solid-state imaging device 100A according to the first embodiment(application example 2) is basically configured in the same way as withthe solid-state imaging device 100A according to the first embodiment(application example 1) except that the minimum line width in thelateral direction is set to not 0.1 μm but 0.2 μm. Along with thismodification of the minimum line width in the lateral direction,adjustment is made regarding the number, widths, boundary distance ofeach of the low refractive index layer 120 _(—) j and high refractiveindex layer 121 _(—) k within the alternate placement layer 112A.

Specifically, with the first embodiment (application example 2), thewidths of the low refractive index layer 120 _(—) j and high refractiveindex layer 121 _(—) k (both are not shown in the drawing) within thealternate placement layer 112A during one cycle of the optical lens110A, and the boundary distance (the synthetic width of the adjacenthigh refractive index layers 121R_4 and 121L_4 in the present example)are set as follows.

high refractive index layer 121R_1+high refractive index layer 121L_1:0.75 μm

high refractive index layer 121R_2, high refractive index layer 121L_2:0.25 μm

high refractive index layer 121R_3, high refractive index layer 121L_3:0.25 μm

high refractive index layer 121R_4+high refractive index layer 121L_4:0.20 μm

low refractive index layer 120R_1, low refractive index layer 120L_1:0.20 μm

low refractive index layer 120R_2, low refractive index layer 120L_2:0.25 μm

low refractive index layer 120R_3, low refractive index layer 120L_3:0.375 μm

FIGS. 3B and 3C are diagrams illustrating the simulation results of theoptical property according to the first embodiment (application example2) shown in FIG. 3A, and represent the results of near-infrared light(λ=780 nm), red light (λ=640 nm), green light (λ=540 nm), and blue light(λ=460 nm), respectively.

As can be understood from these, even in a case wherein the minimum linewidth in the lateral direction is changed from 0.1 μm to 0.2 μm, thenumber, widths, boundary distance of each of the low refractive indexlayer 120 _(—) j and high refractive index layer 121 _(—) k within thealternate placement layer 112A are set appropriately, whereby the lighthaving any wavelength can be condensed with the alternate placementlayer 112A, and a convex lens effect can be provided.

First Embodiment Application Example 3 of Convex Lens

FIGS. 4A through 4C are diagrams for describing a third example(application example 3) of the solid-state imagining device to which theoptical lens according to the first embodiment is applied. Here, FIG. 4Ais the cross-sectional schematic view of the solid-state imaging deviceaccording to the first embodiment (application example 3), and FIGS. 4Band 4C are diagrams illustrating the simulation results of the opticalproperty thereof.

The solid-state imaging device 100A according to the first embodiment(application example 3) is basically configured in the same way as withthe solid-state imaging device 100A according to the first embodiment(application example 1) except that the thickness (substantial lensthickness) of the alternate placement layer 112A is set to not 0.5 μmbut a thinner 0.3 μm. Along with this modification of the lensthickness, adjustment is made regarding the number, widths, boundarydistance of each of the low refractive index layer 120 _(—) j and highrefractive index layer 121 _(—) k within the alternate placement layer112A. With the present example, completely the same adjustment as thatin the first embodiment (application example 1) is made.

Specifically, with the first embodiment (application example 3), thewidths of the low refractive index layer 120 _(—) j and high refractiveindex layer 121 _(—) k (both are not shown in the drawing) within thealternate placement layer 112A during one cycle, and the boundarydistance (the synthetic width of the adjacent low refractive indexlayers 120R_5 and 120L_5 in the present example) are set as follows. Asdescribed above, as to the first embodiment (application example 1), thethickness dimension in the vertical direction is changed from 0.5 μm to0.3 μm, but the width dimension in the lateral direction is the same.

high refractive index layer 121R_1+high refractive index layer 121L_1:0.45 μm

high refractive index layer 121R_2, high refractive index layer 121L_2:0.25 μm

high refractive index layer 121R_3, high refractive index layer 121L_3:0.20 μm

high refractive index layer 121R_4, high refractive index layer 121L_4:0.15 μm

high refractive index layer 121R_5, high refractive index layer 121L_5:0.10 μm

low refractive index layer 120R_1, low refractive index layer 120L_1:0.10 μm

low refractive index layer 120R_2, low refractive index layer 120L_2:0.15 μm

low refractive index layer 120R_3, low refractive index layer 120L_3:0.20 μm

low refractive index layer 120R_4, low refractive index layer 120L_4:0.225 μm

low refractive index layer 120R_5+low refractive index layer 120L_5:0.40 μm

FIGS. 4B and 4C are diagrams illustrating the simulation results of theoptical property according to the first embodiment (application example3) shown in FIG. 4A, and represent the results of near-infrared light(λ=780 nm), red light (λ=640 nm), green light (λ=540 nm), and blue light(λ=460 nm), respectively.

As can be understood from these, even in a case wherein the thickness(substantial lens thickness) of the alternate placement layer 112A ischanged from 0.5 μm to 0.3 μm, the number, widths, boundary distance ofeach of the low refractive index layer 120 _(—) j and high refractiveindex layer 121 _(—) k within the alternate placement layer 112A are setappropriately, whereby the light having any wavelength can be condensedwith the alternate placement layer 112A, and a convex lens effect can beprovided.

First Embodiment Application Example 4 of Convex Lens

FIGS. 5A through 5D are diagrams for describing a fourth example(application example 4) of the solid-state imagining device to which theoptical lens according to the first embodiment is applied. Here, FIG. 5Ais the cross-sectional schematic view of the solid-state imaging deviceaccording to the first embodiment (application example 4), FIG. 5B is amore schematic cross-sectional view, and FIGS. 5C and 5D are diagramsillustrating the simulation results of the optical property thereof.

The solid-state imaging device 100A according to the first embodiment(application example 4) is basically configured in the same way as withthe solid-state imaging device 100A according to the first embodiment(application example 1) except that the pixel size or lens size is setto not 3.6 μm but smaller 1.4 μm. Along with this modification of thepixel size or lens size, adjustment is made regarding the distance(thickness: substantial lens length) from the boundary surface betweenthe silicon substrate 102 and thin-film layer 130 to the alternateplacement layer 112A, the thickness (substantial lens thickness) of thealternate placement layer 112A, and the number, widths, boundarydistance of each of the low refractive index layer 120 _(—) j and highrefractive index layer 121 _(—) k within the alternate placement layer112A.

Specifically, with the first embodiment (application example 4), first,the thickness (substantial lens thickness) of the alternate placementlayer 112A is set to 0.5 μm. One cycle (i.e., lens size) of the opticallens 110A is adjusted to the pixel size (=pixel pitch) of 1.4 μm.

The widths of the low refractive index layer 120 _(—) j and highrefractive index layer 121 _(—) k (both are not shown in the drawing)within the alternate placement layer 112A during one cycle of theoptical lens 110A, and the boundary distance (the synthetic width of theadjacent low refractive index layers 120R_3 and 120L_3 in the presentexample) are set as follows.

high refractive index layer 121R_1+high refractive index layer 121L_1:0.25 μm

high refractive index layer 121R_2, high refractive index layer 121L_2:0.15 μm

high refractive index layer 121R_3, high refractive index layer 121L_3:0.10 μm

low refractive index layer 120R_1, low refractive index layer 120L_1:0.10 μm

low refractive index layer 120R_2, low refractive index layer 120L_2:0.13 μm

low refractive index layer 120R_3+low refractive index layer 120L_3:0.19 μm

Also, with the upper and lower sides of each high refractive indexlayers 121 _(—) k made up of silicon nitride SiN of the alternateplacement layer 112A making up a principal portion of the optical lens110A, a thin film (thickness=0.08 μm) made up of SiON with therefractive index n4 of 1.7 is provided thereto as an antireflection film124 with the same width as each high refractive index layer 121 _(—) k.The antireflection films 124 are thin films made up of an intermediaterefractive index material (SiON with the refractive index of 1.7 in thepresent example) between silicon nitride SiN and silicon oxide SiO2, andare for reducing optical loss due to reflection.

The antireflection films 124 are thin films, and do not affect the lenseffect itself of the alternate placement layer 112A regardless of thethickness and width thereof, regardless of whether or not they areprovided to each high refractive index layer 121 _(—) k. It goes withoutsaying that the antireflection films 124 can be provided to not only thefirst embodiment (application example 4) but also the first embodiment(application examples 1 through 3).

The lens length in the case of providing the antireflection films 124 isdistance from the boundary surface between the silicon substrate 102 andthin-film layer 130 to the antireflection films 124, and is set to 2.3μm in the present example.

FIGS. 5C and 5D are diagrams illustrating the simulation results of theoptical property according to the first embodiment (application example4) shown in FIG. 5A, and represent the results of near-infrared light(λ=780 nm), red light (λ=640 nm), green light (λ=540 nm), and blue light(λ=460 nm), respectively.

As can be understood from these, even in a case wherein the pixel sizeor lens size is changed from 3.6 μm to 1.4 μm, the lens length, and thenumber, widths, boundary distance of each of the low refractive indexlayer 120 _(—) j and high refractive index layer 121 _(—) k within thealternate placement layer 112A are set appropriately, whereby the lighthaving any wavelength can be condensed with the alternate placementlayer 112A, and a convex lens effect can be provided.

First Comparative Example

FIG. 6A is a diagram for describing a first comparative example as tothe convex lens 110A using the alternate placement layer 112A (includingthe alternate placement layer 2A as a single material) included in theoptical lens 110A according to the first embodiment.

The solid-state imaging device 100A according to the first comparativeexample includes a wiring layer 109 above the silicon substrate 102, aninner condensing lens 105 on the upper layer of the wiring layer 109thereof, and a color filter 106 and on-chip lens 108 on the upper layerof the inner condensing lens 105 thereof.

Both the inner condensing lens 105 and on-chip lens 108 are lenseshaving a refractive type lens configuration employing Snell's law.Accordingly, the lens itself is thick such as around 1 μm, andconsequently, the device upper layer serving as the light incident sideof the silicon substrate 102 becomes thick. Thus, undesirable obliqueincident light from the adjacent pixel increases, color mixtures due tothis oblique incident light increase, and accordingly, colorreproducibility becomes poor.

It can also be conceived to perform calculation processing such asmatrix computation to restore color reproducibility, but extra noiseoccurs, and image quality deteriorates.

When reducing the F value of an external image formation system lens,oblique incident light increases due to eclipse caused by metal wiringof the wiring layer 109, so deterioration from ideal sensitivity becomespronounced by the upper layer becoming thick, and accordingly,deterioration in F value light sensitivity is caused wherein theoriginal sensitivity cannot be obtained.

A so-called shading phenomenon also becomes pronounced whereinsensitivity is reduced at the end portion as compared with the center ofthe pixel array unit where the photoelectric conversion units 104 aredisposed in a two-dimensional manner. This is because the principal rayobliquely enters, and accordingly, influence of ellipse increases, forexample.

It can also be conceived that each lens is made into an asymmetric lensshape deformed in the lateral direction so as to correct obliqueincident light to vertical incident light. Note however, from theperspective of a manufacturing process, for example, when fabricatingeach lens with reflow, the fabrication thereof is influenced by gravityor surface tension, so each lens can be fabricated only in a sphericalshape. In other words, a spherical lens is fabricated with reflow, so alens having a configuration deformed in the lateral direction cannot befabricated, and accordingly, a lens whereby oblique incident light canbe corrected to vertical incident light cannot be fabricated.

On the other hand, with each optical lens 110A according to the firstembodiment, the alternate placement layer 112A is configured as aprincipal portion, whereby a convex lens function having a condensingeffect can be realized with an extremely thin lens. Thus, the upperlayer of the device can be thinned, and color mixtures decrease, socolor reproducibility improves, and also extra noise occurrence due tocalculation processing decreases. Also, deterioration in F value lightsensitivity is reduced.

Further, the alternate placement layer 112A serving as a principalportion of the optical lens 110A has a configuration wherein the lowrefractive index layers 120 and high refractive index layers 121 arealternately arrayed with a predetermined width, and can be fabricatedwith just simple easy-to-use processing technology such as lithographytechnology, the RIE (Reactive Ion Etching) method, or the like (detailswill be made later), whereby costs can be suppressed with an easy-to-usefabrication process.

Also, as can be understood from application examples 1 through 4, theconvex lens effect employing the alternate placement layer 112A can bemodified as necessary by adjusting the widths and number of arrays ofeach of the rectangular low refractive index layers 120 and highrefractive index layers 121, and accordingly, the width of designing canoptically spread as compared with a spherical lens.

Second Comparative Example

FIG. 6B is a diagram for describing a second comparative example as tothe convex lens using the alternate placement layer 112A (including thealternate placement layer 2A as a single material) included in theoptical lens 110A according to the first embodiment.

The solid-state imaging device 100A according to the second comparativeexample is described in Japanese Unexamined Patent ApplicationPublication No. 2005-011969. To be brief, an inner condensing lens isconfigured with a Fresnel lens as the basis, which subjects lightsubjected to convergence by an upper portion lens such as an on-chiplens to further convergence to enter this in the correspondingphotoelectric conversion unit.

Specifically, this lens is a refractive type lens, but is configured ina wave type, whereby the lens can be thinned. Note however, this lens isa refractive type, so there is a limit to make the lens thinner than thewavelength order. Also, fabricating such a refractive type makes thefabricating process complicated than a common refractive type lensprocess, and requires further cost. Also, the lens can be fabricatedonly with a spherical surface, so asymmetry cannot be provided thereto.

Additionally, in the case of a Fresnel lens, light obliquely entering ina certain region is not condensed in a point to be condensed originallyin some cases. For example, in FIG. 6B, in a case wherein light entersin the surface portion of a lens as shown in the solid line, the lightis condensed, but in a case wherein light enters in a stepwise wall asshown in the dotted line, the light is refracted or reflected, andaccordingly, the light is not condensed but diffused as shown in thedrawing. This causes condensing efficiency to deteriorate, and moreover,in a case wherein diffused light enters in an adjacent pixel, causes acolor mixture.

Third Comparative Example

FIG. 6C is a diagram for describing a third comparative example as tothe convex lens using the alternate placement layer 112A (including thealternate placement layer 2A as a single material) included in theoptical lens 110A according to the first embodiment.

The solid-state imaging device 100A according to the third comparativeexample is described in Japanese Unexamined Patent ApplicationPublication No. 2006-351972. A condensing element (i.e., convex lens) isconfigured by combining multiple zone regions having a concentricconfiguration divided by a line width equal to or shorter than thewavelength of incident light. Here, of the multiple zone regions, atleast one zone region includes a lower stage light transmission filmhaving a concentric configuration of a first line width and first filmthickness, and an upper stage light transmission film having aconcentric configuration of a second line width and second filmthickness, which is configured above the lower stage light transmissionfilm. To be brief, a condensing element is configured with adistribution refractive index lens having a two-stage concentricconfiguration (i.e., Fresnel lens) as the basis.

Accordingly, the condensing element (convex lens) according to the thirdcomparative example described in Japanese Unexamined Patent ApplicationPublication No. 2006-351972 is a refractive index lens, but isconfigured with a Fresnel lens as the basis, and accordingly, the samesituation occurs as that in the inner condensing lens according to thesecond comparative example described in Japanese Unexamined PatentApplication Publication No. 2005-011969. This situation is shown in FIG.6C, wherein when oblique incident light enters in the steps ofrefractive index around the boundary of each region, the light isreflected or refracted at a wall, and accordingly the light is refractedor reflected, and accordingly, the light is not condensed but diffusedas shown in the drawing. This causes condensing efficiency todeteriorate, and moreover, in a case wherein diffused light enters in anadjacent pixel, causes a color mixture.

On the other hand, with the alternate placement layer 2A (alternateplacement layer 112A) according to the first embodiment, the widths ofthe high refractive index layers 121 having a great refractive index andthe low refractive index layers 120 having a small refractive indexchange gradually within the wavelength order, so there is no step of agreat refractive index such as a Fresnel lens, and there is littlediffusing light caused by reflection or refraction even as to obliqueincident light. Accordingly, deterioration in condensing decreases, solight can be condensed effectively.

Also, the manufacturing process of the alternate placement layer 112A(alternate placement layer 2A) according to the first embodiment is easyto use as compared with the processes of the inner condensing lensaccording to the second comparative example described in JapaneseUnexamined Patent Application Publication No. 2005-011969 and thecondensing element according to the third comparative example describedin Japanese Unexamined Patent Application Publication No. 2006-351972.For example, as can be understood from the configuration shown in FIG.6C, etching is performed with two stages, so the number of processesincreases, and consequently, cost increases. Also, such complicatedetching affects on reproducibility and evenness, and manufacturingirregularities are readily caused.

With the alternate placement layer 112A (alternate placement layer 2A)according to the first embodiment, the high refractive index layers 21(high refractive index layers 121) and low refractive index layers 20(low refractive index layers 120) are arrayed alternately in the lateraldirection, so basically, all that is necessary is deposition of the highrefractive index layers 21 (high refractive index layers 121) andone-time etching, and the subsequent deposition of low refractive indexlayers 20 (low refractive index layers 120) and simple easy-to-useprocessing technology such as lithography technology, RIE method, or thelike, thereby reducing the number of processes, reducing cost, andimproving reproducibility and evenness.

As can be understood from the above description, the principlecompletely differs between the alternate placement layer 2A (alternateplacement layer 112A) according to the first embodiment, which can beconceived such that a condensing lens (i.e., convex lens) utilizing awave surface control arrangement is employed as an inner condensing lens(or surface lens), and the inner condensing lens according to the secondcomparative example (Japanese Unexamined Patent Application PublicationNo. 2005-011969) or the condensing element according to the thirdcomparative example (Japanese Unexamined Patent Application PublicationNo. 2006-351972). With the inner condensing lens according to the secondcomparative example and the condensing element according to the thirdcomparative example, the advantage provided by the alternate placementlayer 2A (alternate placement layer 112A) according to the firstembodiment cannot be accepted.

Fourth Comparative Example

Though not shown in the drawing, with Japanese Unexamined PatentApplication Publication No. 2005-252391, a configuration has beendisclosed wherein a scatterer having a refractive index is provided onthe upper layer within a pixel (referred to as a fourth comparativeexample). Note however, the arrangement of the fourth comparativeexample differs from that in the alternate placement layer 2A (alternateplacement layer 112A) according to the first embodiment such as aconfiguration wherein the high refractive index layers 121 having agreat refractive index are disposed, in a plate shape, densely at thecenter and disposed non-densely farther away from the center, andspecifically, a configuration wherein the widths of the high refractiveindex layers 121 having a great refractive index increase toward thecenter of the lens, i.e., a configuration wherein the center is broad,and the periphery is narrow.

Additionally, the arrangement of the fourth comparative example is not alens function but a low-pass filter function employing scattering effector MTF control function. In this point, with the alternate placementlayer 2A (alternate placement layer 112A) according to the firstembodiment, a feature wherein the velocity of light differs between thehigh refractive index layers 21 (high refractive index layers 121)having a great refractive index and the low refractive index layers 20(low refractive index layers 120) having a small refractive index, andcontinuity of a wave function are combined, thereby accepting a convexlens effect, so the principle and object thereof completely differs fromthe arrangement of the fourth comparative example.

Fifth Comparative Example

Though not shown in the drawing, with Japanese Unexamined PatentApplication Publication No. 2005-203526, a configuration has beendisclosed wherein a refractive index distribution type lens is embeddedin a through hole formed corresponding to a pixel on a lens substrate,which has a refractive index changed in the diameter direction of thethrough hole (referred to as a fifth comparative example). Note however,the arrangement of the fifth comparative example is such that arefractive index distribution is changed gradually in the diameterdirection of the through hole, i.e., lateral direction, and the basicconfiguration concept thereof differs from that in the arrangement ofthe first embodiment wherein a convex lens effect is accepted using thealternate placement layer 2A (alternate placement layer 112A) whichcombines a feature wherein the velocity of light differs between thehigh refractive index layers 21 (high refractive index layers 121)having a great refractive index and the low refractive index layers 20(low refractive index layers 120) having a small refractive index, andcontinuity of a wave function.

With the arrangement of the fifth comparative example, description hasbeen made simultaneously wherein a layer having a great refractive indexand a layer having a small refractive index are deposited in the lateraldirection in order, but in reality, deposition is made not only from thelateral direction but also from underneath, so such a configurationaccording to the first embodiment is not realized, and accordingly, amulti-layer configuration wherein refractive indexes differ only in thelateral direction cannot be readily fabricated.

On the other hand, with the alternate placement layer 112A (alternateplacement layer 2A) according to the first embodiment, the highrefractive index layers 21 (high refractive index layers 121) and lowrefractive index layers 20 (low refractive index layers 120) are arrayedalternately in the lateral direction, so basically, all that isnecessary is deposition of the high refractive index layers 21 (highrefractive index layers 121) and one-time etching, and a multi-layerconfiguration in the vertical direction such as the subsequentdeposition of low refractive index layers 20 (low refractive indexlayers 120) and a process such as lithography technology, RIE method, orthe like, thereby providing an advantage wherein fabrication can be madewith ease to use and a small number of processes.

First Embodiment Modification 1 of Convex Lens

FIGS. 7A and 7B are diagrams for describing a first modification(modification 1) of the optical lens according to the first embodiment.Here, FIG. 7A is the cross-sectional schematic view for describing thesolid-state imaging device according to modification 1 to which theoptical lens according to modification 1 is applied. FIG. 7B is adiagram illustrating the simulation result of the optical propertythereof (λ=540 nm).

With the basic example of the first embodiment, in order to provide aconvex lens function by employing a configuration wherein densityincreases toward the center and density decreases farther away from thecenter, the third convex lens providing method has been employed whereinthe first and second convex lens providing methods are employedtogether, but with modification 1, only the first convex lens providingmethod is employed wherein the width of a layer having a greatrefractive index (high refractive index layer 121 _(—) k) increasesgradually toward the center of the lens. With regard to a layer having asmall refractive index (low refractive index layer 120 _(—) j), all areconfigured so as to have an equal width.

Let us say that the distance (thickness: substantial lens length) fromthe boundary surface between the silicon substrate 102 and thin-filmlayer 130 to the alternate placement layer 112A is 3.6 μm, and thethickness (substantial lens thickness) of the alternate placement layer112A is 0.5 μm. One cycle (i.e., lens size) of the optical lens 110A isadjusted to a pixel size (pixel pitch) of 3.25 μm. This somewhat differsfrom the first embodiment (application example 1) wherein the lens sizeor pixel size is set to 3.6 μm. The pixel size is somewhat changed fromthat in the previous example, but this is for adjustment in the eventthat while the high refractive index layers 121 are set to anappropriate dimension (in increments of 0.05 μm), the low refractiveindex layers 120 are set to be an equal width with an appropriatedimension (in increments of 0.05 μm). An arrangement may be made whereinwhile the pixel size is set to that in the previous example as much aspossible, the low refractive index layers 120 portion is set to be anequal width.

The solid-state imaging device 100A according to the first embodiment(modification 1) is basically configured in the same way as with thesolid-state imaging device 100A according to the first embodiment(application example 1) except that the width of the low refractiveindex layer 120 _(—) j is set to be an equal width. Along with thismodification of changing the width of the low refractive index layer 120_(—) j to an equal width, adjustment is made regarding the number,widths, and boundary distance of each of the low refractive index layer120 _(—) j and high refractive index layer 121 _(—) k within thealternate placement layer 112A.

Specifically, with the first embodiment (modification 1), the widths ofthe low refractive index layer 120 _(—) j and high refractive indexlayer 121 _(—) k (both are not shown in the drawing) within thealternate placement layer 112A during one cycle, and the boundarydistance (the synthetic width of the adjacent low refractive indexlayers 120R_4 and 120L_4 in the present example) are set as follows.

high refractive index layer 121R_1+high refractive index layer 121L_1:0.65 μm

high refractive index layer 121R_2, high refractive index layer 121L_2:0.25 μm

high refractive index layer 121R_3, high refractive index layer 121L_3:0.20 μm

high refractive index layer 121R_4, high refractive index layer 121L_4:0.15 μm

low refractive index layer 120R_1, low refractive index layer 120L_1:0.20 μm

low refractive index layer 120R_2, low refractive index layer 120L_2:0.20 μm

low refractive index layer 120R_3, low refractive index layer 120L_3:0.20 μm

low refractive index layer 120R_4+low refractive index layer 120L_4:0.20 μm

As can be understood from the above settings, the width of the lowrefractive index layer 120 _(—) j having a small refractive index is anequal width of 0.2 μm, and the width of the high refractive index layer121 _(—) k having a great refractive index decreases gradually, such as0.65 μm, 0.25 μm, 0.2 μm, and 0.15 μm, toward the end from the center.

As can be understood from the drawing, with the first embodiment(modification 1) as well, the alternate placement layer 112A of theoptical lens 110A is a condensing element having a SWLL configurationwherein incident light is curved by the periodical structure between thelow refractive index layers 120 made up of silicon oxide SiO2 having arefractive index of 1.46 and the high refractive index layers 121 madeup of silicon nitride having a refractive index of 2.0. With the presentexample, the alternate placement layer 112A is configured such that theminimum line width in the lateral direction of the low refractive indexlayers 120 is 0.20 μm, the minimum line width in the lateral directionof the high refractive index layers 121 is 0.15 μm, and the thickness ofthe lens is 0.5 μm.

FIG. 7B is a diagram illustrating the simulation result of the opticalproperty of the first embodiment (modification 1) shown in FIG. 7A,which is the result of green light (λ=540 nm). As can also be understoodfrom this, even with an arrangement wherein while all widths are set tobe equal regarding the layers having a small refractive index (lowrefractive index layer 120 _(—) j), the widths of the high refractiveindex layers 121 increase gradually toward the center of the lens, thegreen light (λ=540 nm) can be condensed with the alternate placementlayer 112A by setting the number, widths, boundary distance of each ofthe low refractive index layer 120 _(—) j and high refractive indexlayer 121 _(—) k within the alternate placement layer 112Aappropriately, thereby providing a convex lens effect.

Though not shown in the drawing, with regard to near-infrared light(λ=780 nm), red light (λ=640 nm), and blue light (λ=460 nm) as well, thesame convex lens effect is provided.

Thus, the first embodiment (modification 1) is employed, which has aconfiguration wherein the low refractive index layer 120 _(—) j having asmall refractive index has an equal width, and the width of the highrefractive index layer 121 _(—) k increases gradually toward the centerof the lens, whereby a configuration can be realized wherein the highrefractive index layer 121 _(—) k having a great refractive index isdisposed, in a plate shape, densely at the center and disposednon-densely farther away from the center, and accordingly, it can befound that a condensing property exists like the first embodiment (basicexample and application examples 1 through 4 thereof).

With the configuration of the first embodiment (modification 1), thereis provided an advantage wherein fabrication of a lens is facilitated.That is to say, in a case wherein, with a process for embedding the lowrefractive index layers 120, there is difficulty such that embeddingwidths cannot be narrowed due to insufficient lithography resolution, orembedding becomes poor due to occurrence of a void when narrowing theembedding widths, fabrication can be made by setting the widths of thelow refractive index layers 120 to equal widths that can be embeddedusing lithography as with modification 1. Particularly, this becomes aneffective tool when this width that can be embedded is just at thewavelength order, where if the width is expanded further, continuity ofequiphase wave surfaces (wave surfaces) is lost.

First Embodiment Modification 2 of Convex Lens

FIGS. 8A and 8B are diagrams for describing a second modification(modification 2) of the optical lens according to the first embodiment.Here, FIG. 8A is the cross-sectional schematic view for describing thesolid-state imaging device according to modification 2 to which theoptical lens according to modification 2 is applied. FIG. 8B is adiagram illustrating the simulation result of the optical propertythereof (λ=540 nm).

With the basic example of the first embodiment, in order to provide aconvex lens function by employing a configuration wherein densityincreases toward the center and density decreases farther away from thecenter, the third convex lens providing method has been employed whereinthe first and second convex lens providing methods are employedtogether, but with modification 2, only the second convex lens providingmethod is employed wherein the width of a layer having a smallrefractive index (low refractive index layer 120 _(—) j) decreasesgradually toward the center of the lens. With regard to a layer having agreat refractive index (high refractive index layer 121 _(—) k), all areconfigured so as to have an equal width.

Let us say that the distance (thickness: substantial lens length) fromthe boundary surface between the silicon substrate 102 and thin-filmlayer 130 to the alternate placement layer 112A is 3.6 μm, and thethickness (substantial lens thickness) of the alternate placement layer112A is 0.5 μm. One cycle (i.e., lens size) of the optical lens 110A isadjusted to a pixel size (pixel pitch) of 3.85 μm. This somewhat differsfrom the first embodiment (application example 1) wherein the lens sizeor pixel size is set to 3.6 μm. The pixel size is somewhat changed fromthat in the previous example, but this is for adjustment in the eventthat while the low refractive index layers 120 are set to an appropriatedimension (in increments of 0.05 μm), the high refractive index layers121 are set to be an equal width with an appropriate dimension (inincrements of 0.05 μm). An arrangement may be made wherein while thepixel size is set to that in the previous example as much as possible,the high refractive index layers 121 portion is set to be an equalwidth.

The solid-state imaging device 100A according to the first embodiment(modification 2) is basically configured in the same way as with thesolid-state imaging device 100A according to the first embodiment(application example 1) except that the width of the high refractiveindex layer 121 _(—) k is set to be an equal width. Along with thismodification of changing the width of the high refractive index layer121 _(—) k to an equal width, adjustment is made regarding the number,widths, and boundary distance of each of the low refractive index layer120 _(—) j and high refractive index layer 121 _(—) k within thealternate placement layer 112A.

Specifically, with the first embodiment (modification 2), the widths ofthe low refractive index layer 120 _(—) j and high refractive indexlayer 121 _(—) k (both are not shown in the drawing) within thealternate placement layer 112A during one cycle, and the boundarydistance (the synthetic width of the adjacent low refractive indexlayers 120R_5 and 120L_5 in the present example) are set as follows.

high refractive index layer 121R_1+high refractive index layer 121L_1:0.15 μm

high refractive index layer 121R_2, high refractive index layer 121L_2:0.15 μm

high refractive index layer 121R_3, high refractive index layer 121L_3:0.15 μm

high refractive index layer 121R_4, high refractive index layer 121L_4:0.15 μm

high refractive index layer 121R_5, high refractive index layer 121L_5:0.15 μm

low refractive index layer 120R_1, low refractive index layer 120L_1:0.10 μm

low refractive index layer 120R_2, low refractive index layer 120L_2:0.20 μm

low refractive index layer 120R_3, low refractive index layer 120L_3:0.30 μm

low refractive index layer 120R_4, low refractive index layer 120L_4:0.40 μm

low refractive index layer 120R_5+low refractive index layer 120L_5:0.50 μm

As can be understood from the above settings, the width of the highrefractive index layer 121 _(—) k having a great refractive index is anequal width of 0.15 μm, and the width of the low refractive index layer120 _(—) j having a small refractive index increases gradually, such as0.10 μm, 0.20 μm, 0.30 μm, 0.40 μm, and 0.50 μm, toward the end from thecenter.

As can be understood from the drawing, with the first embodiment(modification 2) as well, the alternate placement layer 112A of theoptical lens 110A is a condensing element having a SWLL configurationwherein incident light is curved by the periodical structure between thelow refractive index layers 120 made up of silicon oxide SiO2 having arefractive index of 1.46 and the high refractive index layers 121 madeup of silicon nitride having a refractive index of 2.0. With the presentexample, the alternate placement layer 112A is configured such that theminimum line width in the lateral direction of the high refractive indexlayers 121 is 0.10 μm, the minimum line width in the lateral directionof the high refractive index layers 121 is 0.15 μm, and the thickness ofthe lens is 0.5 μm.

FIG. 8B is a diagram illustrating the simulation result of the opticalproperty of the first embodiment (modification 2) shown in FIG. 8A,which is the result of green light (λ=540 nm). As can also be understoodfrom this, even with an arrangement wherein while all widths are set tobe equal regarding the layers having a great refractive index (highrefractive index layer 121 _(—) k), the widths of the low refractiveindex layers 120 decrease gradually toward the center of the lens, thegreen light (λ=540 nm) can be condensed with the alternate placementlayer 112A by setting the number, widths, boundary distance of each ofthe low refractive index layer 120 _(—) j and high refractive indexlayer 121 _(—) k within the alternate placement layer 112Aappropriately, thereby providing a convex lens effect.

Though not shown in the drawing, with regard to near-infrared light(λ=780 nm), red light (λ=640 nm), and blue light (λ=460 nm) as well, thesame convex lens effect is provided.

Thus, the first embodiment (modification 2) is employed, which has aconfiguration wherein the high refractive index layer 121 _(—) k havinga great refractive index has an equal width, and the width of the lowrefractive index layer 120 _(—) j decreases gradually toward the centerof the lens, whereby a configuration can be realized wherein the highrefractive index layer 121 _(—) k having a great refractive index isdisposed, in a plate shape, densely at the center and disposednon-densely farther away from the center, and accordingly, it can befound that a condensing property exists like the first embodiment (basicexample and application examples 1 through 4 thereof).

With the configuration of the first embodiment (modification 2), thereis provided an advantage wherein fabrication of a lens is facilitated.That is to say, in a case wherein, with a process for etching the highrefractive index layers 121 using lithography, it is difficult toperform narrow width lithography or etching process such that widthscannot be narrowed due to insufficient lithography resolution, or widthcontrollability deteriorates due to occurrence of side etching at thetime of the etching process, fabrication can be made by setting thewidths of the high refractive index layers 121 to equal widths that canbe subjected to etching using lithography as with modification 2.Particularly, this becomes an effective tool when this width that can besubjected to etching using lithography is just at the wavelength order,where if the width is expanded further, continuity of equiphase wavesurfaces (wave surfaces) is lost.

Second Embodiment Convex Lens+Oblique Incident Light Correction(Separate Type)

FIGS. 9 through 10D are diagrams for describing the basic principle ofan optical lens according to a second embodiment. Here, FIG. 9 is adiagram illustrating the simulation result when oblique incident lightenters with the configuration of the first embodiment (e.g., applicationexample 1 in FIG. 2A). FIG. 10A is a diagram illustrating an equiphasewave surface for describing the basic principle of the optical lensaccording to the second embodiment. FIG. 10B is a diagram for describingthe light reception optical system of the solid-state imaging device100A. FIG. 10C is a plan schematic view of a single optical lensaccording to the second embodiment. FIG. 10D is a plan schematic view ina case wherein the optical lens according to the second embodiment isapplied onto the pixel array unit of the solid-state imaging device.Note that, in FIG. 10D, with regard to a lens shape according to thealternate placement layer of each pixel, representative positions aloneare illustrated by being extracted and enlarged from the entire pixelarray unit.

The lens configuration according to the second embodiment has a featurein that a correction mechanism as to incidence of oblique incident lightis provided. A different point as to a later-described third embodimentis that an optical member having an oblique incident light correctionfunction is added to the alternate placement layer 112A having theconvex lens function as a separate member (disposed in another layer).

With the configuration of the first embodiment (e.g., applicationexample 1 in FIG. 2A), when oblique incident light enters, as shown inFIG. 9, it can be found that a condensed position is somewhat shifted inthe lateral direction as the lens center. This is common to a phenomenoncaused even with a normal spherical lens. Accordingly, with theconfiguration of the optical lens according to the first embodiment,there is a possibility that a color mixture problem caused byundesirable oblique incident light entering from an adjacent pixel, or ashading problem wherein deterioration in sensitivity at an end portionof the pixel array unit is caused at an image sensor.

With the configuration of the optical lens according to the secondembodiment, in order to reduce a problem caused by incidence of obliqueincident light, there is provided a correction function for convertingoblique incident light into vertical incident light. The arrangement ofthe correction function thereof has, as shown in FIG. 10A, a feature inthat with the lens center as a boundary, at one side (left side in theillustrated example) many high refractive index layers 21 having a greatrefractive index exist by ratio, and at the opposite side (right side inthe illustrated example) a few high refractive index layers 21 exist byratio. It goes without saying that the present embodiment differs fromthe above-mentioned first embodiment in that the left and right of thelens are asymmetric.

In order to provide a correction function as to incidence of obliqueincident light by employing a configuration wherein with the lens centeras a boundary, at one side (left side in the illustrated example) manyhigh refractive index layers 21 having a great refractive index exist byratio, and at the opposite side (right side in the illustrated example)a few high refractive index layers 21 exist by ratio, for example, whenfocusing on the high refractive index layers 21, a first obliqueincident light correction method can be employed assuming that thewidths of the high refractive index layers 21 having a great refractiveindex increase gradually in one direction (at the left side in theillustrated example) at one cycle of the optical lens (i.e., lens size).Conversely, when focusing on the low refractive index layers 20, asecond oblique incident light correction method can also be employedassuming that the widths of the low refractive index layers 20 having asmall refractive index increase gradually in one direction (at the rightside in the illustrated example) at one cycle of the optical lens (i.e.,lens size). Further, a third oblique incident light correction methodcan also be employed wherein the first and second oblique incident lightcorrection methods are employed together. From the perspective ofcorrection efficiency, it is most effective to employ the third obliqueincident light correction method.

The optical lens according to the second embodiment has a function forconverting oblique incident light into vertical incident light (referredto as an incident angle conversion function), so differs from alater-described third embodiment in that the center of gravity ofasymmetry becomes the end portion of the optical lens (the center of thehigh refractive index layer 21L_4 at the left end in FIG. 10A). Notethat description will be made at the third embodiment regarding thedefinition of “center of gravity”.

In other words in view of the configuration description of alater-described third embodiment, the first oblique incident lightcorrection method is a method assuming a configuration wherein thewidths of the high refractive index layers 21 having a great refractiveindex increase gradually toward the optical center of gravity position(the other end side of the lens in the present example) from one endside of the member (lens: alternate placement layer 2B). Similarly, inother words in view of the configuration description of alater-described third embodiment, the second oblique incident lightcorrection method is a method assuming a configuration wherein thewidths of the low refractive index layers 20 having a small refractiveindex decreases gradually toward the optical center of gravity position(the other end side of the lens in the present example) from one endside of the member (lens: alternate placement layer 2B). As can also beunderstood from this description, with regard to the fundamental policyof the incident angle conversion function, there is no differencebetween the second and third embodiments.

First, as shown in FIG. 10A, let us say that there are provided several(six of 1_1 through 1_6 in the drawing) plate-shaped single materiallayers 1 having a refractive index n0 alone exist at the light outputside, and adjacent thereto (specifically, layer 1_6) a plate-shapedlayer (referred to as an alternate placement layer) 2B where rectangularlayers (referred to as low refractive index layers) 20 having therefractive index n0 and rectangular layers (referred to as highrefractive index layers) 21 having a refractive index n1 higher(greater) than the refractive index n0 (n1>n0) are arrayed alternatelyin the lateral direction. Though not shown in the drawing, it may beconceived that a plate-shaped single material layer having therefractive index n0 alone is provided at the light incident side of thealternate placement layer 2B. Though details will be described later,the alternate placement layer 2B serves as an optical lens function forconverting oblique incident light into vertical incident light.

With the arrangement of the basic example of the second embodiment shownin the drawing, as a configuration is employed wherein at the left sideas to the center CL many high refractive index layers 21 having a greatrefractive index exist by ratio, and at the right side a few highrefractive index layers 21 exist by ratio, the widths of the highrefractive index layers 21L_1 through 21L_4 at the left side areconfigured so as to decrease gradually toward the center CL, and thewidths of the high refractive index layers 21R_1 through 21R_4 at theright side are configured so as to increase gradually toward the centerCL, and the widths of the high refractive index layers 21 having a greatrefractive index are configured so as to increase gradually in onedirection from right to left.

Additionally, the widths of the low refractive index layers 20L_1through 20L_3 at the left side are configured so as to increasegradually toward the center CL, and the widths of the low refractiveindex layers 20R_1 through 20R_3 at the right side are configured so asto decrease gradually toward the center CL, and the widths of the lowrefractive index layers 20 having a small refractive index areconfigured so as to decrease gradually in one direction from right toleft.

That is to say, with the basic example of the second embodiment, theabove-mentioned third oblique incident light correction method isemployed wherein the above-mentioned first and second oblique incidentlight correction methods are employed together. Thus, as shown in thedrawing, oblique incident light can be converted into vertical incidentlight.

With the comparison as to the alternate placement layer 2A according tothe first embodiment shown in FIG. 1B, with the lens center of thealternate placement layer 2A as a boundary, employing only oneconfiguration (right side alone in the example shown in the drawing) ofthe left and right configurations is equivalent to the alternateplacement player 2B according to the second embodiment. With thealternate placement layer 2A according to the first embodiment, afunction for converting the route of incident light into the center sideis activated at the left and right with the lens center as a boundary,and it can be conceived that employing only one side of the functionthereof is equivalent to the alternate placement layer 2B according tothe second embodiment.

Such an alternate placement layer 2B is applied to the solid-stateimaging device 100A by being disposed at the light incident side orlight emission side or both thereof of the alternate placement layer 2A,whereby a function can be realized wherein a condensed point of theconvex lens function is moved to the center of a pixel or above thephotoelectric conversion unit 104 in a sure manner.

With the lens configuration according to the second embodiment, thealternate placement layer 2B having such an incident angle conversionfunction for converting oblique incident light into vertical incidentlight is layered on the alternate placement layer 2A according to thefirst embodiment which serves as an optical lens function having acondensing effect. At this time, there may be employed a configurationwherein the alternate placement layer 2B is disposed at the lightincident side, i.e., a configuration wherein the alternate placementlayer 2B having the incident angle conversion function is layered abovethe alternate placement layer 2A having the convex lens function.

Alternatively, there may be employed a configuration wherein thealternate placement layer 2A is disposed at the light incident side,i.e., a configuration wherein the alternate placement layer 2B havingthe incident angle conversion function is layered below the alternateplacement layer 2A having the convex lens function. Further, there maybe employed a configuration the alternate placement layer 2B is disposedboth at the light incident side and at the light emission side, i.e., aconfiguration wherein the alternate placement layer 2B having theincident angle conversion function is layered both above and below ofthe alternate placement layer 2A having the convex lens function.

If oblique incident light can be converted into vertical incident light,there can be solved a color mixture problem wherein light enters from anadjacent pixel, and a shading problem wherein deterioration insensitivity becomes pronounced at the end portion of the pixel arrayunit.

For example, in the event that this effect is applied to the solid-stateimaging device 100A, as shown in FIG. 10B, the principal ray from animage formation lens assumes oblique incidence when the incidentposition is closer to the end portion of the pixel array unit, so thiseffect becomes more effective by weakening an oblique correctionfunction at the center of the pixel array unit, and enhancing thecorrection function toward the end portion of the pixel array unit. Forexample, the closer the incident position is to the end portion of thepixel array unit, the higher the asymmetry of rate of the highrefractive index layers 21 having a great refractive index is.

As can be clearly understood from the configuration shown in FIG. 10A,the lens thickness thereof is the thickness of the alternate placementlayer 2B where the rectangular high refractive index layer 21 _(—) khaving a great refractive index and the rectangular low refractive indexlayer 20 _(—) j having a small refractive index are arrayed alternatelyin the lateral direction, whereby an extremely thin incident angleconversion lens (oblique light correction lens) can be provided. Forexample, the thickness of the lens can be reduced to 0.5 μm or less.

With a plan configuration also, the alternate placement layer 2B needsto have a configuration wherein, with the lens center as a boundary, atone side many high refractive index layers 21 having a great refractiveindex exist by ratio, and at the opposite side a few high refractiveindex layers 21 exist by ratio, and as long as this is satisfied,various types of plan configuration can be employed.

For example, as shown in FIG. 10C, there may be employed a configurationwherein the linear low refractive index layers 20 and linear highrefractive index layers 21 are arrayed by being shifted to one side witha predetermined width. Also, though not shown in the drawing, there maybe employed curved low refractive index layers 20 and curved highrefractive index layers 21.

In the event that the alternate placement layer 2B is applied to thepixel array unit of the solid-state imaging device 100A in combinationwith the alternate placement layer 2A serving as a convex lens,incidence of oblique incident light causes no problem at the center ofthe pixel array unit, so there is no need to provide the alternateplacement layer 2B at the center thereof. On the other hand, incidenceof oblique incident light causes a problem the closer the incidentposition is to the end portion of the pixel array unit. Therefore, asshown in FIG. 10D, for example, the alternate placement layer 2B havinga configuration wherein the linear low refractive index layers 20 andlinear high refractive index layers 21 are arrayed by being shifted toone side with a predetermined width such as shown in FIG. 10C isdisposed such that the optical axis faces the center of the pixel arrayunit.

At this time, an arrangement needs to be made wherein the incident angleconversion function is enhanced the closer the incident position is tothe end portion of the pixel array unit, and the change level of rate ofthe low refractive index layers 20 and high refractive index layers 21is enhanced the closer the incident position is to the end portion ofthe pixel array unit. That is to say, it is desirable to provide aconfiguration wherein there is no asymmetry at the center of the pixelarray unit, and asymmetry is enhanced the closer the incident positionis to the end portion of the pixel array unit.

Here, the example is shown in a case wherein the photoelectricconversion elements (light reception portions) are arrayed in atwo-dimensional manner, but this can also be applied to a case whereinthe photoelectric conversion elements (light reception portions) arearrayed in a one-dimensional manner.

Thus, oblique incidence of the principal ray is corrected the closer theincident position is to the end portion of the pixel array unit, wherebythe condensed point of each convex lens according to the alternateplacement layer 2A can be brought to the center of a pixel. Such a lensshape is provided within the solid-state imaging device 100B (i.e.,formed integral with the solid-state imaging device 100B), wherebydeterioration in sensitivity (shading) caused at the end portion of thepixel array unit can be reduced without proving a pupil correctionmechanism, and color mixtures can be reduced, and accordingly, colorreproducibility can be improved.

Second Embodiment Application Example of Incident Angle ConversionFunction

FIGS. 11A and 11B are diagrams for describing a solid-state imagingdevice to which the optical lens according to the second embodiment isapplied. Here, FIG. 11A is a cross-sectional schematic view of asolid-state imaging device to which the alternate placement layer 2Bhaving the incident angle conversion function is applied, and FIG. 11Bis a diagram illustrating the simulation result of the optical propertythereof.

As shown in FIG. 11A, the solid-state imaging device 100B according tothe second embodiment is provided with the solid-state imaging device100A according to comparative example 1 of the alternate placement layer2A according to the first embodiment shown in FIG. 2A as the base, andfurther includes an optical lens 110B where an alternate placement layer112B having the incident angle conversion function (oblique correctionfunction) is disposed at the light incident side (under space) of thealternate placement layer 112A having the convex lens function. Thus,the optical lens 110B according to the second embodiment is configuredso as to include the convex lens function by the alternate placementlayer 112A and the oblique correction function by the alternateplacement layer 112B separately.

The placement relation between the alternate placement layer 112A andalternate placement layer 112B shown in FIG. 11A is illustrated in acase wherein light enters from the lower right side of space. Note thatthe center of an incident angle conversion lens (oblique lightcorrection lens) according to the alternate placement layer 112B issomewhat shifted to the right side of space as to the center of a convexlens according to the alternate placement layer 112A.

With the second embodiment (application example), of the optical lens110B, the widths of the low refractive index layer 120 _(—) j and highrefractive index layer 121 _(—) k (both are not shown in the drawing)within the alternate placement layer 112B during one cycle (pixelsize=3.6 μm) are set as follows.

high refractive index layer 121R_4: 0.45 μm

high refractive index layer 121R_3: 0.35 μm

high refractive index layer 121R_2: 0.25 μm

high refractive index layer 121R_1+high refractive index layer 121L_1:0.20 μm

high refractive index layer 121L_2: 0.15 μm

high refractive index layer 121L_3: 0.11 μm

high refractive index layer 121L_4: 0.10 μm

low refractive index layer 120R_3: 0.10 μm

low refractive index layer 120R_2: 0.12 μm

low refractive index layer 120R_1: 0.185 μm

low refractive index layer 120L_1: 0.235 μm

low refractive index layer 120L_2: 0.260 μm

low refractive index layer 120L_3: 0.345 μm

low refractive index layer 120L_4: 0.745 μm

FIG. 11B is a diagram illustrating the simulation result of the opticalproperty of the second embodiment (application example) shown in FIG.11A, which is the result of the oblique incident light of green light(λ=540 nm) being entered in the solid-state imaging device 100B. As canalso be understood from this, the alternate placement layer 112B, whichhas a configuration wherein, with the lens center as a boundary, at oneside many high refractive index layers 121 having a great refractiveindex exist by ratio, and at the opposite side a few high refractiveindex layers 121 exist by ratio, is disposed so as to be superimposed onthe alternate placement layer 112A, whereby the oblique incident lightof green light can be condensed generally at the center of the convexlens according to the alternate placement layer 112A. This means that anoblique correction function according to the incident angle conversionfunction works effectively.

Though omitted in the drawing, with regard to near-infrared light (λ=780nm), red light (λ=640 nm), and blue light (λ=460 nm) as well, there issimilarly an oblique correction function effect wherein oblique incidentlight is condensed generally at the center of the convex lens accordingto the alternate placement layer 2A.

The convex lens function according to the alternate placement layer 112Aand the incident angle conversion function (oblique correction function)according to the alternate placement layer 112B are included in thesolid-state imaging device 100B, whereby oblique incident light can beconverted into vertical incident light, shading and color mixtures canbe reduced, and high image quality can be achieved.

Third Embodiment Convex Lens+Oblique Incident Light Correction(Integrated Type)

FIGS. 12A through 12H are diagrams for describing the basic principle ofan optical lens according to a third embodiment. Here, FIG. 12A is adiagram illustrating an equiphase wave surface for describing the basicprinciple of the optical lens according to the third embodiment. FIG.12B is a diagram for describing the center of gravity of a lens, andFIGS. 12C through 12H are plan schematic views of the optical lensaccording to the third embodiment.

The lens configuration according to the third embodiment has a featurein that a correction mechanism as to incidence of oblique incident lightis provided, and is common to the second embodiment in this point. Adifferent point as to the above-mentioned embodiment is that there isemployed an alternate placement layer combining both of the convex lensfunction and oblique incident light correction function.

As shown in FIG. 12A, the basic concept of an alternate placement layer2C according to the third embodiment is to apply the arrangement of thealternate placement layer 2B according to the second embodiment havingan asymmetric configuration wherein, with the lens center as a boundary,at one side many high refractive index layers having a high refractiveindex exist by ratio, and at the opposite side few high refractive indexlayers exist by ratio, with the alternate placement layer 2A having asymmetric configuration wherein the layers having a great refractiveindex are disposed, in a plate shape, densely at the center and disposednon-densely farther away from the center as the base.

That is to say, the alternate placement layer 2C according to the thirdembodiment has a feature in that the convex lens function and incidentangle conversion function (oblique incident light correction function)are included simultaneously by including a configuration wherein thelayers having a great refractive index of which the widths are equal toor smaller than the wavelength order are disposed, in a plate shape,densely at the center and disposed non-densely farther away from thecenter, and including an asymmetric configuration in the lateraldirection as to the lens center.

A configuration is included wherein the widths of the high refractiveindex layers 21 having a great refractive index increase graduallytoward asymmetric center of gravity, as viewed from either side ofcenter of gravity. Also, a configuration is included wherein widths ofthe low refractive index layers 20 having a small refractive indexdecrease gradually toward asymmetric center of gravity. A difference asto the first embodiment is in that at one side of the left and rightsides the array of the low refractive index layers 20 and highrefractive index layers 21 are disposed non-densely, and at the otherside are disposed densely as to the center of gravity of the lens.

In order to apply an asymmetric configuration to the alternate placementlayer 2A having a symmetric configuration, for example, a firstasymmetrization method can be employed assuming a configuration whereinthe widths of the high refractive index layers 21 having a greatrefractive index increase gradually toward the optical center of gravityposition from one end portion side of a member (lens: alternateplacement layer 2C), i.e., a configuration wherein the widths of thehigh refractive index layers 21 having a great refractive index increasegradually toward asymmetric center of gravity.

Alternatively, a second asymmetrization method can be employed assuminga configuration wherein the widths of the low refractive index layers 20having a small refractive index decrease gradually toward the opticalcenter of gravity position from one end portion side of the member(lens: alternate placement layer 2C), i.e., a configuration wherein thewidths of the low refractive index layers 20 having a small refractiveindex decrease gradually toward asymmetric center of gravity.Alternatively, a third asymmetrization method can be employed whereinthe first and second asymmetrization methods are employed together. Fromthe perspective of efficiency of asymmetrization, it is most effectiveto employ the third asymmetrization method.

Now, description will be made regarding “center of gravity” withreference to FIG. 12B. Within a pixel matrix or certain area face, letus say that the refractive index of the high refractive index layers 21having a great refractive index is n1, and the refractive index of thelow refractive index layers 20 having a small refractive index is n0. Ina case wherein, with the (x, y) coordinates within a plane, thefollowing Expression (1) holds, the position (x1, y1) thereof is definedas optical center of gravity.

$\begin{matrix}{{\int{\int_{D}{\left( {x_{1} - x} \right)\left( {y_{1} - y} \right){f\left( {x,y} \right)}\ {x}{y}}}} = 0} & (1)\end{matrix}$

This means that integration of the primary moment of a surroundingrefractive index is 0 at the center of gravity position. FIG. 12Billustrates a conceptual diagram of a center of gravity position in thecase of one dimension, but in reality, the center of gravity position istwo dimensions, so becomes (x, y) coordinates, and simultaneously, aposition satisfying a condition wherein integration of (x, y) becomes 0is center of gravity in two dimensions.

In the case of the first embodiment, a symmetric configuration isincluded wherein the high refractive index layers 21 having a greatrefractive index are disposed densely at the center and disposednon-densely farther away from the center, so center of gravity isidentical to the mechanical center of the lens. In the case of thesecond embodiment, it can be conceived that only one side of the leftand right of the first embodiment having a symmetric configuration isused, and accordingly, the end portion of the optical lens is center ofgravity, i.e., asymmetric center of gravity.

On the other hand, in the case of the third embodiment, the secondembodiment is applied to the first embodiment having a symmetricconfiguration such that the rate of the high refractive index layers 21having a great refractive index is asymmetrical at the left and rightthereof, so center of gravity is shifted as to the mechanical center ofthe lens, and becomes asymmetric center of gravity. This is alsoapparent from the plan schematic views shown in FIGS. 12C through 12H.

That is to say, it goes without saying that with a plan configuration aswell, the alternate placement layer 2C according to the third embodimentthere employs a configuration wherein the second embodiment is appliedto the first embodiment. For example, in the case of employing acircular configuration similar to the alternate placement layer 2Aaccording to the first embodiment, as for the shape of each of the highrefractive index layer 21 _(—) k having a great refractive index and lowrefractive index layer 20 _(—) j having a small refractive index, anarbitrary shape can be employed, such as a circle, ellipse, regularsquare, rectangle, triangle, or the like. Subsequently, of these shapes,a circular shape should be formed of shapes as can be regarded as thesame or different shapes such that the width of each ring differsgradually between the left and right sides at not the lens center butthe center of gravity as a boundary.

For example, FIG. 12C corresponds to FIG. 1C, wherein an asymmetriccircle or circular ring shape is employed such that each of the highrefractive index layer 21 _(—) k and low refractive index layer 20 _(—)j has a circle or circular ring shape, and as for the width of eachring, with the lens center as a boundary, at the left side the lowrefractive index layers 20 decreases gradually toward the lens center,and the high refractive index layers 21 increases gradually towardcenter of gravity, and at the right side the low refractive index layers20 decreases gradually toward center of gravity, and the high refractiveindex layers 21 increases gradually toward the lens center, and eachwidth and change level thereof differ at both sides.

FIG. 12D corresponds to FIG. 1D, wherein an asymmetric ellipse orelliptical circular shape is employed. FIG. 12E corresponds to FIG. 1E,wherein an asymmetric regular square or square circular shape isemployed. FIG. 12F corresponds to FIG. 1F, wherein an asymmetricrectangle or rectangular circular shape is employed.

It goes without saying that the total condensing effects of therespective lenses are affected with the plan configuration of thealternate placement layer 2A, i.e., the plan configuration regarding howthe high refractive index layers 21 and low refractive index layers 20are arrayed, so in the case of applying this to a solid-state imagingdevice, it is desirable to adjust the shape of the plan configurationexemplified in FIGS. 12C through 12F, particularly the shape of the highrefractive index layer 21_1 of center of gravity to the plan shape ofthe light reception portion.

Also, the function for converting oblique incident light into verticallight exists at either side as to center of gravity, so a configurationemploying any one side as to center of gravity can also be employed. Forexample, as shown in FIG. 12G, there may be employed a configurationwherein as to the plan layout shown in FIG. 12C, a part of the circularlow refractive index layer 20 _(—) j having a small refractive index orcircular high refractive index layer 21 _(—) k having a great refractiveindex is missing, so a circular shape cannot be formed. Alternatively,as shown in FIG. 12H, there may be employed a configuration wherein asto the plan layout shown in FIG. 12E, a part of the rectangular lowrefractive index layer 20 _(—) j having a small refractive index orrectangular high refractive index layer 21 _(—) k having a greatrefractive index is missing, so a circular shape cannot be formed.

In the case of applying to the pixel array unit of the solid-stateimaging device 100C, there is no problem due to incidence of obliqueincident light at the center of the pixel array unit, so at the centerthereof there is no need to provide an oblique light correction effect.On the other hand, incidence of oblique incident light causes a problemthe closer the incident position is to the end portion of the pixelarray unit. Therefore, there is a need to provide an arrangement suchthat the incident angle conversion function is enhanced the closer theincident position is to the end portion of the pixel array unit, and thechange level of rate of the low refractive index layers 20 and highrefractive index layers 21 is enhanced the closer the incident positionis to the end portion of the pixel array unit.

That is to say, it is desirable to employ a configuration wherein thereis no asymmetry at the center of the pixel array unit, and asymmetry isenhanced the closer the incident position is to the end portion of thepixel array unit. The other side of the coin is that it is desirable toemploy a configuration wherein the position of an asymmetric center ofgravity position is shifted in the center direction of the pixel arrayunit from the center of a pixel (photoelectric conversion unit, lightreception portion) the closer the incident position is to the endportion of the pixel array unit.

Here, the example is shown in a case wherein the photoelectricconversion elements (light reception portions) are arrayed in atwo-dimensional manner, but this can also be applied to a case whereinthe photoelectric conversion elements (light reception portions) arearrayed in a one-dimensional manner.

Thus, similar to the second embodiment, oblique incidence of theprincipal ray is corrected the closer the incident position is to theend portion of the pixel array unit, whereby the condensed point of eachconvex lens according to the alternate placement layer 2A can be broughtto the center of a pixel. Such a lens shape is provided within thesolid-state imaging device 100C (i.e., formed integral with thesolid-state imaging device 100C), whereby deterioration in sensitivity(shading) caused at the end portion of the pixel array unit can bereduced, color mixtures can be reduced, and accordingly, colorreproducibility can be improved. Additionally, the convex lens effectand oblique light correction effect are realized by the single alternateplacement layer 2C, whereby the configuration can be reduced in size.

Third Embodiment Application Example 1 of Convex Lens Function+IncidentAngle Conversion Function

FIGS. 13A and 13B are diagrams for describing a first example(application example 1) of a solid-state imaging device to which theoptical lens according to the third embodiment is applied. Here, FIG.13A is the cross-sectional schematic view of the solid-state imagingdevice according to the third embodiment (application example 1), andFIG. 13B is a diagram illustrating the simulation result of the opticalproperty thereof.

As shown in FIG. 13A, the solid-state imaging device 100C according tothe third embodiment (application example 1) is provided with thesolid-state imaging device 100A according to comparative example 4 ofthe alternate placement layer 2A according to the first embodiment shownin FIG. 5A as the base, wherein the pixel size and lens size are 1.4 μm.

With the third embodiment (application example), of the optical lens110C, the widths of the low refractive index layer 120 _(—) j and highrefractive index layer 121 _(—) k (both are not shown in the drawing)within the alternate placement layer 112C during one cycle are set asfollows.

high refractive index layer 121R_1+high refractive index layer 121L_1:0.25 μm

high refractive index layer 121R_2: 0.10 μm

high refractive index layer 121L_2: 0.15 μm

high refractive index layer 121L_3: 0.10 μm

low refractive index layer 120R_1: 0.14 μm

low refractive index layer 120L_1: 0.155 μm

low refractive index layer 120L_2: 0.195 μm

Also, with the upper and lower sides of each high refractive indexlayers 121 _(—) k made up of silicon nitride SiN of the alternateplacement layer 112C making up a principal portion of the optical lens110C, a thin film (thickness=0.08 μm) made up of SiON with therefractive index n4 of 1.7 is provided thereto as an antireflection film124 with the same width as each high refractive index layer 121 _(—) k.This point is similar to the application example 4 of the firstembodiment.

FIG. 13B is a diagram illustrating the simulation result of the opticalproperty of the third embodiment (application example 1) shown in FIG.13A, which is the result of oblique incident light of green light (λ=540nm) entering in the solid-state imaging device 100C. As can also beunderstood from this, even in the case of employing a single alternateplacement layer 112C including both of the arrangement of the alternateplacement layer 112A according to the first embodiment having the convexlens function and the arrangement of the alternate placement layer 112Baccording to the second embodiment having the oblique incident angleconversion function (light correction function), the oblique incidentlight of green light can be condensed generally at the center of theconvex lens according to the alternate placement layer 112C. This meansthat an oblique correction function according to the incident angleconversion function works effectively.

Though omitted in the drawing, with regard to near-infrared light (λ=780nm), red light (λ=640 nm), and blue light (λ=460 nm) as well, there issimilarly an oblique correction function effect wherein oblique incidentlight is condensed generally at the center of the convex lens accordingto the alternate placement layer 2C.

The alternate placement layer 112C including both of the convex lensfunction and incident angle conversion function (oblique correctionfunction) is included in the solid-state imaging device 100C, wherebyoblique incident light can be converted into vertical incident light,shading and color mixtures can be reduced, and high image quality can beachieved.

Currently, normal lenses for image sensors are fabricated with reflow,but the shape of the lens always becomes a spherical shape due tosurface tension, and accordingly, a lens with asymmetry cannot befabricated. Accordingly, such effects cannot be obtained.

Third Embodiment Application Example 2 (CMOS Response)

FIGS. 14A through 14C are diagrams for describing a second example(application example 2) of a solid-state imaging device to which theoptical lens according to the third embodiment is applied. Here, FIGS.14A and 14B are circuit diagrams of the solid-state imaging deviceaccording to the third embodiment (application example 2). FIG. 14C is aplan schematic view of an alternate placement layer applied to the pixelarray unit in the solid-state imaging device according to the thirdembodiment (application example 2). Note that, in FIG. 14C, with regardto a lens shape according to the alternate placement layer of eachpixel, representative positions alone are illustrated by being extractedand enlarged from the entire pixel array unit.

The solid-state imaging device according to the third embodiment(application example 2) is a solid-state imaging device applied to aCMOS sensor, and hereafter, will be referred to a CMOS solid-stateimaging device 201. In this case, a configuration is provided wherein asingle cell amplifier is provided as to each pixel (particularly,photoelectric conversion element) within the pixel array unit. A pixelsignal is amplified at the corresponding cell amplifier, and is thenoutput through a noise canceling circuit or the like.

As shown in FIG. 14A, the CMOS solid-state imaging device 201 is aso-called typical column type, which includes a pixel array unit 210where multiple pixels 211 including a light reception element (anexample of a charge generating unit) for outputting a signalcorresponding to the amount of incident light are arrayed in a matrixmanner, wherein the signal output from each pixel 211 is a voltagesignal, and a CDS (Correlated Double Sampling) processing function unit,a digital conversion unit (ADC: Analog Digital Converter), and so forthare provided in column parallel.

Specifically, as shown in the drawing, the CMOS solid-state imagingdevice 201 includes the pixel array unit 210 where the multiple pixels211 are arrayed in a matrix manner, a driving control unit 207 providedon the outside of the pixel array unit 210, a column processing unit226, and an output circuit 228.

The driving control unit 207 has a control circuit function for readingout the signals of the pixel array unit 210 sequentially. For example,as the driving control unit 207, there are provided a horizontalscanning circuit (column scanning circuit) 212 for controlling columnaddresses and column scanning, a vertical scanning circuit (row scanningcircuit) 214 for controlling row addresses and row scanning, acommunication and timing control unit 220 having functions, such as aninterface function as to an external device, and a function forgenerating an internal clock.

The horizontal scanning circuit 212 has a function of a readout scanningunit for reading out a count value from the column processing unit 226.These respective components of the driving control unit 207 are formedintegral with semiconductor regions such as single-crystal silicon usingthe same technology as semiconductor integrated circuit manufacturingtechnology along with the pixel array unit 210, and are configured assolid-state imaging devices (imaging devices) serving as an example of asemiconductor system.

In FIG. 14A, a part of rows and columns is omitted from the drawing forconvenience, but in reality, several tens to several thousands of pixels211 are disposed at each row and each column. This pixel 211 isconfigured of a photoelectric conversion element 212 also referred to asa light reception element (charge generating unit), and intrapixelamplifier (cell amplifier; pixel signal generating unit) 205 having asemiconductor device (e.g., transistor) for amplification. As for theintrapixel amplifier 205, for example, an amplifier having a floatingdiffusion amplifier configuration is employed.

The pixels 211 are connected to the vertical scanning unit 214 via a rowcontrol line 215 for selecting a row, and the column processing unit 226via a vertical signal line 219, respectively. Here, the row control line215 indicates overall wiring entering the pixels from the verticalscanning circuit 214.

The horizontal scanning circuit 212 and vertical scanning circuit 214are configured so as to include a shift register or decoder for example,and start address selection operation (scanning) in response to acontrol signal provided from the communication and timing control unit220. Therefore, various pulse signals (e.g., reset pulse RST, transferpulse TRF, DRN control pulse DRN, and so forth) for driving the pixels211 are included in the row control line 215.

Though not shown in the drawing, the communication and timing controlunit 220 includes a timing generator TG (an example of a readout addresscontrol device) function block for supplying a clock necessary foroperation of each component, and a predetermined timing pulse signal,and a communication interface function block for receiving a masterclock CLK0 via a terminal 220 a, receiving data DATA for instructing anoperation mode or the like via a terminal 220 b, and further outputtingdata including the information of the CMOS solid-state imaging device201 via a terminal 220 c.

The pixels are arrayed in a two-dimensional matrix manner, so it isdesirable to perform vertical scanning reading by accessing andcapturing an analog pixel signal output in the column direction via thevertical signal line 219 generated by the intrapixel amplifier (pixelsignal generating unit) 205 in increments of row (in column parallel),and then to perform horizontal scanning reading by accessing in the rowdirection which is a vertical column array direction to read out a pixelsignal (e.g., digitized pixel data) to the output side, therebyrealizing speeding up of the pixel signal and pixel data. It goeswithout saying that not only scanning reading but also random access canbe performed by directly addressing a desired pixel 211 to read out onlythe information of the necessary pixel 211.

The communication and timing control unit 220 supplies a clock CLK1having the same frequency as the master clock CLK0 input via theterminal 220 a, a clock obtained by dividing the clock CLK1 by two, or alow-speed clock by further dividing the clock CLK1 to each componentwithin the device, such as the horizontal scanning circuit 212, verticalscanning circuit 214, column processing unit 226, and so forth.

The vertical scanning circuit 214 selects a row of the pixel array unit210, and supplies a necessary pulse to the row thereof. The verticalscanning circuit 214 includes, for example, a vertical decoder forstipulating a readout row in the vertical direction (selecting a row ofthe pixel array unit 210), and a vertical driving circuit for supplyinga pulse the row control line 215 corresponding to the pixel 211 on thereadout address (row direction) stipulated by the vertical decoder todrive this. Note that the vertical decoder selects a row for electronicshutter or the like as well as a row for reading a signal.

The horizontal scanning circuit 212 selects an unshown column circuitwithin the column processing unit 226 in sync with the low-speed clockCLK2 sequentially, and guides the signal thereof to the horizontalsignal line (horizontal output line) 218. For example, the horizontalscanning circuit 212 includes, for example, a horizontal decoder forstipulating a readout column in the horizontal direction (selecting eachcolumn circuit within the column processing unit 226), and a horizontaldriving circuit for guiding each signal of the column processing unit226 to the horizontal signal line 218 using a selection switch 227 inaccordance with the readout address stipulated by the horizontaldecoder. Note that as for the number of horizontal signal lines 218, forexample, n number of bits (n is a positive integer) handled by a columnAD circuit, specifically, for example, if 10 (=n) bits, there aredisposed ten horizontal signal lines 218 corresponding to the number ofbits thereof.

With the CMOS solid-state imaging device 201 having such aconfiguration, the pixel signals output from the pixels 211 are suppliedto the column circuits of the column processing unit 226 via thevertical signal lines 219 in increments of vertical column.

Each column circuit of the column processing unit 226 receives onecolumn worth of pixel signals, and processes the signals thereof. Forexample, each column circuit has an ADC (Analog Digital Converter)circuit for converting an analog into signal 10-bit digital data, forexample, using the low-speed clock CLK2.

The column processing unit 226 can have a noise canceling function bydevising the circuit configuration thereof, whereby the pixel signal ofthe voltage mode input via the vertical signal line 219 can be subjectedto processing for obtaining the difference between a signal level (noiselevel) immediately after pixel rest and a true (corresponding to lightreception amount) signal level Vsig. Thus, noise signal componentscalled fixed pattern noise (FPN) or reset noise can be removed.

The analog pixel signal (or digital pixel data) processed at the columnprocessing unit 226 is transmitted to the horizontal signal line 218 viaa horizontal selection switch 217 which is driven by the horizontalselection signal from the horizontal scanning circuit 212, and furtherinput to the output circuit 228. Note that the above-mentioned 10 bitsare an example, other number of bits may be employed, such as less than10 bits (e.g., 8 bits), the number of bits exceeding 10 bits (e.g., 14bits), or the like.

According to such a configuration, a pixel signal is sequentially outputregarding each vertical column for each row from the pixel array unit210 where the pixels 211 serving as charge generating units are disposedin a matrix manner. Subsequently, one image, i.e., a frame imagecorresponding to the pixel array unit 210 where the light receptionelements are disposed in a matrix manner, is indicated with a pixelsignal group of the entire pixel array unit 210.

FIG. 14B illustrates a configuration example of an imaging device 200using the CMOS solid-state imaging device 201. The imaging device 200 isemployed for a camera (or camera system) or a portable device includingan imaging function or the like, for example. This is also similar to alater-described imaging device 300.

The pixel signal derived from the output circuit 228 as CMOS output(Vout) is input to an image signal processing unit 240 shown in FIG.14B. A control signal from a central control unit 242 configured of aCPU (Central Processing Unit), ROM (Read Only Memory), RAM (RandomAccess Memory), and so forth is input to the driving control unit (anexample of a driving unit) 207 of the CMOS solid-state imaging device201, and the image signal processing unit 240 provided at the subsequentstage of the CMOS solid-state imaging device 201. The driving controlunit 207 determines driving timing based on the control signal from thecentral control unit 242. The pixel array unit 210 (specifically,transistors making up the pixels 211) of the CMOS solid-state imagingdevice 201 is driven based on a driving pulse from the driving controlunit 207.

The central control unit 242 controls the driving control unit 207, andalso controls signal processing, image output processing, and so forthat the image signal processing unit 240.

The image signal processing unit 140 performs, for example, ADconversion processing for digitizing the imaging signals R, G, and B ofeach pixel, synchronization processing for synchronizing digitizedimaging data R, G, and B, vertical banding noise correction processingfor correcting vertical banding noise components caused by smearphenomenon and blooming phenomenon, WB control processing forcontrolling white balance (WB) adjustment, gamma correction processingfor adjusting a gradation level, dynamic range expanding processing forexpanding a dynamic range by using the pixel information of two screenshaving different charge storage time, YC signal generation processingfor generating luminance data (Y) and color data (3), or the like. Thus,an image based on primary color imaging data of red (R), green (G), andblue (B) (each piece of pixel data of R, G, and B) can be obtained.

Each image thus generated is transmitted to an unshown display unit, andis presented to an operator as a visible image, or is stored and savedas is in a storage device such as a hard disk device or the like, or istransmitted to another function unit as processed data.

Now, with the CMOS solid-state imaging device 201 according to the thirdembodiment (Application Example 2), an alternate placement layer 2 isprovided above the pixel array unit 210 such that the lens centercorresponds to each pixel 211. The plan state thereof is set to such asshown in FIG. 14C.

That is to say, first, as for the alternate placement layer 2, it isfundamental to employ the circular or circular ring shapes of the highrefractive index layer 21 _(—) k and low refractive index layer 20 _(—)j, such as shown in FIGS. 1C and 12C. Subsequently, the alternateplacement layer 2 is disposed such that the optical axis thereof facesthe center of the pixel array unit 210. At this time, an arrangementneeds to be made wherein the incident angle conversion function isenhanced the closer the incident position is to the end portion of thepixel array unit 210, and the change level of rate of the low refractiveindex layers 20 and high refractive index layers 21 is enhanced thecloser the incident position is to the end portion of the pixel arrayunit 210. That is to say, it is desirable to provide a configurationwherein the alternate placement layer 2A shown in FIG. 1C having noasymmetry is employed at the center of the pixel array unit 210, and thealternate placement layer 2C shown in FIG. 12C is employed at the otherportion and the asymmetry thereof is enhanced the closer the incidentposition is to the end portion of the pixel array unit 210. In short, aconfiguration is employed wherein symmetric circular or circular ringshapes are provided at the center of the pixel array unit 210, and moreasymmetric shapes are provided the closer the incident position is tothe end portion of the pixel array unit 210.

The asymmetric center of gravity position at that time is shifted in thecenter direction of the pixel array unit 210, and the amount of shiftingis set so as to increase the closer the incident position is to the endportion of the pixel array unit 210. Thus, oblique incidence of theprincipal ray is corrected the closer the incident position is to theend portion of the pixel array unit 210, whereby the condensed point ofeach lens can be brought to the center of the corresponding pixel 211.We have found that such lens shapes are provided within the CMOSsolid-state imaging device 201 (above the pixel array unit 210), wherebydeterioration in sensitivity (shading) caused at the end portion of thepixel array unit 210 is reduced, and color mixtures decrease, andaccordingly, color reproducibility improves.

Third Embodiment Application Example 3 (CCD Response)

FIGS. 15A through 15D are diagrams for describing a third example(application example 3) of a solid-state imaging device to which theoptical lens according to the third embodiment is applied. Here, FIGS.15A and 15B are circuit diagrams of the solid-state imaging deviceaccording to the third embodiment (application example 3). FIG. 15C is across-sectional structural diagram around the substrate surface of thesolid-state imaging device according to the third embodiment(application example 3). FIG. 15D is a plan schematic view of analternate placement layer applied to the pixel array unit in thesolid-state imaging device according to the third embodiment(application example 3). Note that, in FIG. 15D, with regard to a lensshape according to the alternate placement layer of each pixel,representative positions alone are illustrated by being extracted andenlarged from the entire pixel array unit.

The solid-state imaging device according to the third embodiment(application example 3) is a solid-state imaging device applied to a CCDsolid-state imaging device (IT_CCD image sensor) employing the interlinetransfer method, and hereafter, will be referred to a CCD solid-stateimaging device 301.

As shown in FIG. 14A, the CCD solid-state imaging device 301 includes apixel array unit 310 where multiple pixels 311 including a lightreception element (an example of a charge generating unit) foroutputting a signal corresponding to the amount of incident light arearrayed in a matrix manner (i.e., a two-dimensional matrix manner). Thepixel array unit 310 specifically includes a photoelectric conversionelement 312 also called a light reception element (charge generatingunit) for outputting a signal corresponding to the amount of incidentlight.

Also, multiple vertical transfer CCDs 322 for vertically transferringthe signal charge generated at the photoelectric conversion element 312are provided in the vertical transfer direction. The charge transferdirection of the vertical transfer CCDs 322, i.e., the readout directionof a pixel signal is the vertical direction (X direction in thedrawing).

With the configuration of the CCD solid-state imaging device 301 shownin FIG. 15A, only several pixels 311 are illustrated, but in reality,this is repeated in the lateral direction, and the result thereof isfurther repeated in the vertical direction.

Further, a MOS transistor making up a readout gate 324 lies between thevertical transfer CCD 322 and each photoelectric conversion element 312,and an unshown channel stop is provided at the boundary portion of eachunit cell (increment component).

A pixel matrix unit 310 serving as an imaging area is configured of themultiple vertical transfer CCDs 322, which are provided for eachvertical row of the pixels 311, for vertically transferring signalcharge read out by the readout gate 324 from each pixel 311.

The signal charge accumulated in the photoelectric conversion element312 of the pixel 311 is read out to the vertical transfer CCD 322 of thesame vertical row by a driving pulse φROG corresponding to a readoutpulse ROG being applied to the readout gate 324. The vertical transferCCD 322 is transfer-driven, for example, by a drive pulse φVx based on avertical transfer clock Vx such as three phases through eight phases,and transfers a portion equivalent to one scanning line (one line) ofthe readout signal charge in the vertical direction (referred to as lineshifting) at a time in order during a part of a horizontal blankingperiod.

Also, with the CCD solid-state imaging device 301, one line worth of ahorizontal transfer CCD 326 (H register portion, horizontal transferportion) adjacent to each transfer destination side end portion of themultiple vertical transfer CCDs 322, i.e., the vertical transfer CCD 322of the last row, extending in a predetermined (e.g., horizontal)direction is provided. The horizontal transfer CCD 326 istransfer-driven, for example, by drive pulses φH1 and φH2 based ontwo-phase horizontal transfer clocks H1 and H2, and transfers one lineworth of signal charge transferred from the multiple vertical transferCCDs 322 in the horizontal direction in order during a horizontalscanning period after a horizontal blanking period. Accordingly,multiple horizontal transfer electrodes corresponding to two-phasedriving are provided.

With the end portion of the transfer destination of the horizontaltransfer CCD 326, for example, there is provided an output amplifier 328including a charge voltage conversion unit having a floating diffusionamplifier (FDA). The output amplifier 328 converts the signalhorizontally transferred by the horizontal transfer CCD 326 into avoltage signal sequentially at the charge voltage conversion unit,amplifies this to a predetermined level, and output this. A pixel signalis derived from this voltage signal as CCD output (Vout) according tothe incident amount of light from a subject. Thus, the CCD solid-stateimaging device 301 employing the interline transfer method isconfigured.

The pixel signal derived from the output amplifier 328 as CCD output(Vout) is input to the image signal processing unit 340 shown in FIG.15B. An image switching control signal from a central control unit 342serving as an example of a signal switching control unit is input to theimage signal processing unit 340. The CCD solid-state imaging device 301is driven based on a drive pulse from a driving control unit (an exampleof a driving unit) 307.

FIG. 15B illustrates a configuration example of the imaging device 300when employing the CCD solid-state imaging device 301. Basically, thisconfiguration is the same as the configuration shown in FIG. 14B exceptthat the imaging device is replaced from the CMOS solid-state imagingdevice 201 to the CCD solid-state imaging device 301.

Now, with the CCD solid-state imaging device 301 according to the thirdembodiment (application example 3), an alternate placement layer 2 isprovided above the pixel array unit 310 such that the lens centercorresponds to the center of each pixel 311. That is to say, a lensconfiguration employing the alternate placement layer 2 exists withinthe imaging device.

For example, FIG. 15C illustrates a cross-sectional structural diagramof the substrate surface and vicinity. With the pixels 311 for receivingincident light, an optical lens made up of an alternate placement layeris provided as an inner condensing lens corresponding to thephotoelectric conversion element 312 made up of PN junction, andthereon, a color filter and on-chip lens are provided.

FIG. 15D illustrates the plan state thereof. Fundamentally, the sameconcept as the case of the CMOS solid-state imaging device 201 shown inFIG. 14C is applied. First, as for the alternate placement layer 2, itis fundamental to employ the rectangular or rectangular ring shapes ofthe high refractive index layer 21 _(—) k and low refractive index layer20 _(—) j, such as shown in FIGS. 1E and 12E. Subsequently, thealternate placement layer 2 is disposed such that the optical axisthereof faces the center of the pixel array unit 310. At this time, itis desirable to provide a configuration wherein the alternate placementlayer 2A shown in FIG. 1E having no asymmetry is employed at the centerof the pixel array unit 310, and the alternate placement layer 2C shownin FIG. 12E is employed at the other portion and the asymmetry thereofis enhanced the closer the incident position is to the end portion ofthe pixel array unit 310. In short, a configuration is employed whereinsymmetric rectangular or rectangular ring shapes are provided at thecenter of the pixel array unit 310, and more asymmetric shapes areprovided the closer the incident position is to the end portion of thepixel array unit 310.

The asymmetric center of gravity position at that time is shifted in thecenter direction of the pixel array unit 310, and the amount of shiftingis set so as to increase the closer the incident position is to the endportion of the pixel array unit 310. Thus, oblique incidence of theprincipal ray is corrected the closer the incident position is to theend portion of the pixel array unit 310, whereby the condensed point ofeach lens can be brought to the center of the corresponding pixel 311.We have found that such lens shapes are provided within the CCDsolid-state imaging device 301 (above the pixel array unit 310), wherebydeterioration in sensitivity (shading) caused at the end portion of thepixel array unit 310 is reduced, and color mixtures decrease, andaccordingly, color reproducibility improves and a high image qualitydevice can be obtained.

Third Embodiment Modification of Convex Lens+Incident Angle Conversion

With the basic example of the third embodiment, in order to apply anasymmetric configuration to the alternate placement layer 2A having ansymmetric configuration, the third asymmetrization method has beenemployed wherein the first and second asymmetrization methods areemployed together, but only one thereof may be employed. This point iscommon to the first embodiment, wherein a convex lens providing methodis not restricted to the third convex lens providing method foremploying the first and second convex lens providing methods together,and may be configured of only one of the first and second convex lensproviding methods.

For example, though not shown in the drawing, modification 1 can beprovided by applying only the first asymmetrization method assuming aconfiguration wherein the widths of great refractive index layers (highrefractive index layer 21 _(—) k) increase toward asymmetric center ofgravity. In this case, as for small refractive index layers, all thewidths need to be set to an equal width. In this case as well, even asviewed from either side of center of gravity, a configuration isprovided wherein the width of the high refractive index layer 21 _(—) khaving a great refractive index increases gradually toward asymmetriccenter of gravity.

Also, though not shown in the drawing, modification 2 can be provided byapplying only the second asymmetrization method assuming a configurationwherein the widths of small refractive index layers (low refractiveindex layer 20 _(—) j) decrease toward asymmetric center of gravity. Inthis case, as for great refractive index layers (high refractive indexlayer 21 _(—) k), all the widths need to be set to an equal width. Inthis case as well, a configuration is provided wherein the width of thelow refractive index layer 20 _(—) j having a small refractive indexdecreases gradually toward asymmetric center of gravity.

Fourth Embodiment Fundamentals of Concave Lens

FIG. 16 is a diagram for describing the basic principle of a fourthembodiment of an optical lens. Here, FIG. 16 is a diagram illustratingequiphase wave surfaces for describing the basic principle of the fourthembodiment.

With the above-mentioned first through third embodiments, the convexlens function having a condensing effect is included in the alternateplacement layers 2A through 2C, but this fourth embodiment has a featurein that a concave lens function having a diffusion effect is included inan alternate placement layer 2D.

In order to include a concave lens function having a diffusion effect inthe alternate placement layer 2D, with the fourth embodiment, asymmetric configuration is employed wherein great refractive indexlayers having a width equal to or smaller than the wavelength order aredisposed, in a plate shape, non-densely at the center and disposeddensely farther away from the center. That is to say, the relationbetween the widths of the great refractive index layers and the widthsof the small refractive index layers is inverted as to the firstembodiment, whereby a concave lens function can be included in thealternate placement layer 2D.

In order to include a concave lens function by providing a configurationwherein density is low at the center and increases farther away from thecenter, for example, it is desirable to employ one of a first concavelens proving method wherein the widths of great refractive index layersdecrease gradually toward the center of a lens, a second concave lensproviding method wherein widths of small refractive index layersincrease gradually toward the center of a lens, and a third concave lensproviding method wherein the first concave lens providing method andsecond concave lens providing method are employed together.

From the perspective of diffusion efficiency, it is most effective toemploy the third concave lens providing method. In this case, the waveface is a convex face, whereby diffusibility of light can be included.

Also, in a case wherein, with a process for embedding low refractiveindex layers, there is difficulty such that embedding widths cannot benarrowed due to insufficient lithography resolution, or embeddingbecomes poor due to occurrence of a void when narrowing the embeddingwidths, fabrication can be made by setting the widths of the lowrefractive index layers to equal widths that can be embedded usinglithography like the fourth embodiment (modification 1). Particularly,this becomes an effective tool when this width that can be embedded isjust at the wavelength order, where if the width is expanded further,continuity of equiphase wave surfaces (wave surfaces) is lost.

Also, in a case wherein, with a process for etching high refractiveindex layers using lithography, it is difficult to perform narrow widthlithography or etching process such that widths cannot be narrowed dueto insufficient lithography resolution, or width controllabilitydeteriorates due to occurrence of side etching at the time of theetching process, fabrication can be made by setting the widths of thehigh refractive index layers to equal widths that can be subjected toetching using lithography like the fourth embodiment (modification 2).Particularly, this becomes an effective tool when this width that can besubjected to etching using lithography is just at the wavelength order,where if the width is expanded further, continuity of equiphase wavesurfaces (wave surfaces) is lost.

As for the advantage of such a concave lens, for example, a recessedportion formed by subjecting the high refractive index layer 21 _(—) kto etching on a wiring layer including multiple wires is embedded withthe low refractive index layer 20 _(—) j, whereby an inner diffusionlens (concave lens) can be formed as to each photoelectric conversionunit (light reception portion), and accordingly, the inner diffusionlens can be disposed at an appropriate position without depending onirregularities of wiring. Thus, incident light can be condensed at aphotoelectric conversion unit in a most appropriate manner.

When the center of an inner diffusion lens is formed so as to be biasedtoward the center side of the pixel array unit (imaging area) from thecenter of a photoelectric conversion unit, shading due to obliqueincident light is improved, and pupil correction can be performed. Atleast one of the multiple lenses is an on-chip lens formed above theinner diffusion lens, whereby incident light can be condensed at a lightreception portion in collaboration with the on-chip lens serving as acondensing lens and the inner diffusion lens.

With the fourth embodiment as well, like the second embodiment, thealternate placement layer 2B having the incident angle conversionfunction (oblique light correction function) can be combined with thealternate placement layer 2D having the convex lens function. Also, likethe third embodiment, the alternate placement layer 2D which includesboth of the concave lens function and oblique incident light correctionfunction can be provided by applying the arrangement of the alternateplacement layer 2B according to the second embodiment having anasymmetric configuration wherein, with the lens center as a boundary, atone side many high refractive index layers having a great refractiveindex exist by ratio, and at the opposite side a few high refractiveindex layers exist by ratio.

As can be understood from the above-mentioned description, whenproviding a function as an optical member by arraying the low refractiveindex layer 20 _(—) j and high refractive index layer 21 _(—) k of whichthe widths are equal to or smaller than the wavelength order in thelateral direction, the layout relation of each piece of density of thehigh refractive index layer 21 _(—) k at the lens center and end portionis adjusted, whereby the convex lens function (condensability) can beprovided, and the convex lens function (expandability) can be provided.The present embodiment can be applied to an optical device, such as thesolid-state imaging device 100, a display, and so forth by providingcondensability or expandability.

<Manufacturing Process>

FIG. 17A is a conceptual diagram for describing the manufacturingprocess according to the present embodiment in a case wherein thealternate placement layer 2 (2A through 2D) according to the firstthrough fourth embodiments is formed integral with the solid-stateimaging device. FIGS. 17B and 17C are conceptual diagrams for describingcomparison examples as to the manufacturing process according to thepresent embodiment. Here, FIG. 17B illustrates an inner lensmanufacturing process, and FIG. 17C illustrates an on-chip lensmanufacturing process.

In a case wherein the alternate placement layer 2 (2A through 2D)according to the first through fourth embodiments is formed integralwith the solid-state imaging device, first, silicon oxide SiO2(refractive index n1=1.46) making up a single material layer 3 servingas the medium of the optical lens 110 is formed with predeterminedthickness on the upper layer of the silicon substrate (not shown in thedrawing) where the pixel units have already been formed. A siliconnitride SiN thin film making up the thin-film layer 130 is formed on theupper layer of the silicon substrate (not shown in the drawing) asnecessary, and on the upper layer thereof silicon oxide SiO2 making upthe single material 3 serving as the medium of the optical lens 110 isformed with predetermined thickness. Now, the predetermined thicknessmeans the distance (substantial lens length) from the surface of thesilicon substrate to later-described silicon nitride SiN making up thealternate placement layer 2.

Subsequently, as shown in (1) in FIG. 17A, the silicon nitride SiNmaking up the alternate placement layer 2 is layered with predeterminedthickness on the upper layer of the single material 3 made up of siliconoxide SiO2. Now, the predetermined thickness means the thickness of thealternate placement layer 2, i.e., lens thickness.

Subsequently, as with a resist coating process shown in (2) in FIG. 17A,a resist film is formed on the upper layer of the alternate placementlayer 2 made up of silicon nitride SiN. Further, like exposure anddevelopment processes shown in (3) in FIG. 17A, the resist film isexposed using a resist pattern such that each of the low refractiveindex layer 20 _(—) j and high refractive index layer 21 _(—) k having apredetermined width which is changed gradually is arrayed inpredetermined order, and the portion corresponding to the portionserving as the low refractive index layer 20 _(—) j is removed (etching)from the resist film. It goes without saying that the array position ofeach of the low refractive index layer 20 _(—) j and high refractiveindex layer 21 _(—) k is set to a position corresponding to the positionof a pixel (particularly, light reception portion).

There is provided a single material layer 3 made up of silicon oxideSiO2 having the thickness corresponding to the lens length between thesilicon nitride making up the alternate placement layer 2 and theunshown silicon substrate, so a problem due to damage by etching up tonear the silicon substrate surface is not caused.

Subsequently, as with an opening (RIE processing) process shown in (4)in FIG. 17A, etching is performed using the RIE (Reactive Ion Etching)method through the opening portion of the resist film corresponding tothe portion serving as the low refractive index layer 20 _(—) j, therebyproviding opening portions on the silicon nitride SiN of the alternateplacement layer 2, which reach the SiO2 film of the lowermost layer.

Subsequently, as with a resist removal process shown in (5) in FIG. 17A,the resist film on the silicon nitride SiN making up the alternateplacement layer 2 is removed. Thus, the alternate placement layer 2where the opening portion is formed at the portion serving as the lowrefractive index layer 20 _(—) j is formed on the upper layer of thesingle material layer 3 made up of silicon oxide SiO2.

Further, in the case of applying to an inner lens, for planarizing orthe like, as with an embedding process shown in (6) in FIG. 17A, asilicon oxide SIO2 film which serves as the low refractive index layer20 _(—) j and serves as protection of the alternate placement layer 2 isformed with predetermined thickness on the upper layer of the singlematerial layer 3 made up of silicon oxide SiO2 where the alternateplacement layer 2 where the opening portion is formed at the portionserving as the low refractive index layer 20 _(—) j is formed, forexample, using CVD or the like again. Thus, the portion serving as thelow refractive index layer 20 _(—) j of the alternate placement layer 2made up of silicon nitride SiN where the opening portions are formed isembedded by silicon oxide SiO2, and a single material 1 of silicon oxideSiO2 serving as a medium at the light incident side is formed withpredetermined thickness.

Though not shown in the drawing, further thereon a color filer or microlens may be formed so as to correspond to a pixel.

On the other hand, in the case of applying to an on-chip lens to bedisposed on a color filter, the embedding process shown in (6) in FIG.17A is unnecessary.

Note that, of the manufacturing process shown here, with the embeddingprocess, not only the portion serving as the low refractive index layer20 _(—) j is embedded by silicon oxide SiO2, but also a silicon oxideSiO2 film is formed on the upper layer of the alternate placement layer2 where the low refractive index layer 20 _(—) j and high refractiveindex layer 21 _(—) k are alternately disposed, thereby forming a singlematerial layer 1, but forming the single material layer 1 is notindispensable. Also, in extreme cases, the entire embedding process canbe omitted. In this case, the opening portions provided in siliconnitride SiN are not embedded by silicon oxide SiO2, so the lowrefractive index layer 20 _(—) j is the air.

In any case, an on-chip lens employing the arrangement of the alternateplacement layer 2 is formed on the uppermost layer of the imagingdevice. In this case, in reality, the surface thereof comes into contactwith the air.

Thus, the manufacturing process according to the present embodimentincludes no reflow process, and fabrication can be made only by simpleand easy-to-use processing technology of lithography and etching,whereby an easy-to-use process having no complicated process such asetchback or the like can be provided, and not only reduction in thenumber of processes and reduction in cost are realized, but alsoadvantages of reproducibility, uniformity, and mass productivity can beobtained.

Further, each of the low refractive index layer 20 _(—) j and highrefractive index layer 21 _(—) k having a predetermined width which ischanged gradually can be arrayed in predetermined order, by design ofthe photoresist mask. A lens effect according to the alternate placementlayer 2 can be changed as appropriate by adjusting the width and numberof arrays of each rectangular low refractive index layer 20 _(—) j andeach rectangular high refractive index layer 21 _(—) k. An asymmetricconfiguration can be readily fabricated in the in-plane direction, andaccordingly, the width of designing can optically spread as comparedwith a case wherein an existing spherical lens is manufactured.

On the other hand, with the manufacturing process of the comparativeexample shown in FIG. 17B, in the case of forming an inner lens, first,as shown in (1) in FIG. 17B, silicon nitride SiN serving as the mediumof a lens is formed on silicon oxide SiO2 with predetermined thickness.The predetermined thickness is a level somewhat thicker than thethickness of the ultimate inner lens.

Next, as with a resist coating process shown in (2) in FIG. 17B, aresist film is formed on the upper layer of a lens medium layer.Further, as with an exposure and development process shown in (3) inFIG. 17B, a resist pattern such as lenses being arrayed in predeterminedorder is employed to exposure the resist film, and remove the portioncorresponding to the portion equivalent to between the resist film andan adjacent lens (etching).

Subsequently, as with a reflow process shown in (4) in FIG. 17B, resistis solved to form a lens shape. For example, resist is solved (reflowed)by setting postbake to 150° C., thereby forming a lens shape.Accordingly, as for resist, a heat-proof weak material is necessary.

Subsequently, as with an etchback (RIE processing) process shown in (5)in FIG. 17B, etching is performed using the RIE (Reactive Ion Etching)method, thereby removing resist. Thus, as shown in (6) in FIG. 17B, aconvex lens is formed on a lens medium layer. At this time, there is apossibility that a problem may be caused wherein gain enters (adepository film is formed) to narrow a gap between lenses.

Subsequently, in order to flatten a surface, as with an embeddingprocess shown in (7) in FIG. 17B, a silicon oxide SiO2 film is formedwith predetermined thickness. Though not shown in the drawing, furtherthereon a color film or micro lens may be formed so as to correspond toa pixel.

On the other hand, in the case of forming an on-chip lens to be disposedon a color filter, first, as shown in (1) in FIG. 17C, a polymericmaterial such as OPV or the like serving as a lens medium is formed withpredetermined thickness on the upper layer of a color filter to beformed further on the upper layer above the silicon substrate 102. Thepredetermined thickness is a level somewhat thicker than the thicknessof the ultimate inner lens.

Hereafter, in the same way as that in the case of forming theabove-mentioned inner lens, the processes up to the etchback (RIEprocessing) process shown in (5) in FIG. 17C are performed, therebyforming a convex lens, as shown in (6) in FIG. 17C.

In the case of applying to an on-chip lens, the embedding process shownin (6) in FIG. 17B according to inner lens formation is unnecessary.Note however, for the sake of surface protection or the like, apolymeric material having a low refractive index may be further embeddeddepending on cases.

Thus, with the manufacturing process according to the comparativeexample, a convex lens is formed by reflow and etchback regardless ofwhether to form an inner lens or on-chip lens. With reflow of resistserving as the origin of a lens shape, in order to fabricate a sphericalshape using surface tension, an asymmetric configuration cannot beprovided within a surface. Also, the number of processes increases, andcost increases.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

1. A manufacturing method of an optical member comprising the steps of:forming the films of any one of high refractive index layers having agreat refractive index and low refractive index layers having a lowrefractive index; forming a plurality of opening portions by arraying inthe lateral direction of said films; and embedding each of said openingportions with the others of said high refractive index layers and saidlow refractive index layers; thus manufacturing an optical member wheresaid high refractive index layers and said low refractive index layersare disposed alternately in the lateral direction as to an optical axis.2. A manufacturing method of a solid-state imaging device comprising thesteps of: forming low refractive index layers having a small refractiveindex on a semiconductor substrate where a light reception portion isformed; forming high refractive index layers having a great refractiveindex on said low refractive index layers; forming a plurality ofopening portions at positions corresponding to said light receptionportions of said refractive index layers by arraying said plurality ofopening portions; and embedding each of said opening portions with saidlow refractive index layers; thus manufacturing an optical member wheresaid high refractive index layers and said low refractive index layersare disposed alternately in the lateral direction as to an optical axis,integral with said semiconductor substrate.